This south Vieques beach might not sound like much, but it's one of travelers' favorite experiences in Puerto Rico. During the day, Mosquito Bay is nothing special as Caribbean beaches go. At night, the waters emit a blue glow from organisms called dinoflagellates that live in the waters and light up when disturbed by boats, paddles or hands dipped in the water. Hundreds of thousands of bioluminescent dinoflagellates live in each gallon of bay water, and the light show put on by these tiny creatures provide is truly a (natural) wonder to behold.

Avoid visiting the bay during a full moon, since the moonlight somewhat spoils the display. Recent travelers recommended going out in a kayak to get the full effect of the glow. Some note that the bay isn't as bright as they hoped.

U.S. News Insider Tip: Many visitors flock to Old San Juan for nightlife, but you'll find more locals in La Placita de Santurce, a farmer's market by day that hums with music, dancing, dining, and drinking at night. – Robert Curley

Viejo San Juan is home to a variety of top attractions, including the Castillo San Felipe del Morro (a.k.a. El Morro) and the Castillo San Cristóbal, the two centuries-old forts guarding the walled city of San Juan. Within the walls you'll find Calle del Cristo, one of Old San Juan's most popular shopping and entertainment districts, and Calle de la Fortaleza, which regularly has art dangling from above. While most visitors take advantage of seeing the historic and iconic sights, wandering the narrow streets and plazas of Old San Juan is an experience in itself. Many of the best tours in Puerto Rico include strolls through the old town's cobblestone streets to view the historic, colorful architecture and experience Puerto Rico's vibrant culture. No need to leave for lunch: Old San Juan is bursting with street vendors and restaurants ready to satiate your appetite. At night, the city comes alive and is filled with a bustling nightlife known for its drinks and Latin dancing.

El Morro, which sits within the San Juan National Historic Site, juts out of San Juan harbor and beckons to cruise ships. Construction of the hulking, six-story fortress started in 1539. It was originally built to deter sea attacks, and went on to withstand two world wars and several other battles under the control of the Spanish and, later, the United States. Now, El Castillo San Felipe del Morro (known simply as El Morro) is Puerto Rico's go-to tourist attraction, both for its extensive history and its outstanding vistas of the Atlantic Ocean. You can also walk through the fortress' depths, which include a maze of tunnels, barracks and prison cells. Exhibitions and a park film offer a more in-depth look at the fort's history, and park rangers are stationed around the site to answer questions and lead interpretative programs. A photo in one of the fort's iconic watchtowers is the ultimate Puerto Rico selfie stop.

You'll enjoy exploring more if you wear comfortable walking shoes, as the fort is quite large: it can take up to three hours to explore the whole place on foot. Travelers tend to agree the El Morro is worth visiting whether you're a history buff or not but for a little guidance on the fort's history, consider signing up for one of the best tours in Puerto Rico.

If you really want to get away from it all, and a trip to Vieques or Culebra doesn't quite scratch that itch, consider a visit to Culebrita. This mile-long coral island, the easternmost point of Puerto Rico, sits offshore of Culebra. Part of the Culebra National Wildlife Refuge, the island is largely uninhabited other than by pelicans, green sea turtles and other wildlife. Daytrippers who come over from Culebra to bask on the Culebrita's half-dozen or so beaches, including the aptly named Playa Tortuga, home to nesting sea turtles. The beaches typically have clear waters and soft white sand. The island also has a number of tidal pools that are popular swimming holes for visitors who disembark from tour boats at a dock on West Beach; Turtle Beach is about a 15-minute walk from the boat dock.

Culebrita Lighthouse is one of the few manmade objects on the island; raised by the Spanish in 1886, the now decommissioned beacon guided ships through the Virgin Passage and Vieques Sound.

On the island of Culebra, which sits about 20 miles east of Puerto Rico, visitors will find a beach perfect for families, snorkelers and those looking for a remote spot that boasts a delightful aesthetic from nearly every angle. Flamenco Beach's 1-1/2-mile strip of sand is the most popular on Culebra and is often recognized by travelers and experts as the most beautiful in all of Puerto Rico.

Facilities like bathrooms and showers can be found on-site, and the beach's white sand is peppered with kiosks selling refreshments or offering chairs and umbrellas for rent (about $10 each). Amenities and tranquility are part of the allure of Flamenco Beach, but above all else, travelers simply can't stop raving about the beach's beauty. Some travelers do complain that Flamenco Beach's popularity means it can get a bit crowded on the weekends (despite a lack of upscale resorts or restaurants).  One unusual highlight of the beach is several rusting battle tank hulks in the surf — a reminder that Culebra was once a bombing range for the U.S. military.

U.S. News Insider Tip: The piña colada cocktail was born in 1954 at San Juan's Caribe Hilton. Visitors to the hotel's Caribar can order the original recipe drink as well as more modern takes on this classic poolside refresher. – Robert Curley

A visit to Puerto Rico wouldn't be complete without tasting one of its best-known beverages: rum. The spirit, derived from sugar cane, is one of Puerto Rico's top exports and the island is often referred to as the "rum capital of the world." There are many kinds of rum from traditional white rum to dark rum as well as several producers, including Bacardí, Don Q, Ron de Barrelito, and PitoRico, a smaller brand.

Nicknamed for a notorious Puerto Rican pirate, this town on the southwest coast of Puerto Rico is known for the unspoiled and protected beaches of the Cabo Rojo National Wildlife Refuge and the 5,000-acre Boquerón State Forest, both of which have hiking trails as well as beautiful shorelines. Combate Beach in Boquerón is a particular favorite for sunsets and jumping off the pier.

The picturesque Los Morrilos Lighthouse (located in the Cabo Rojo National Wildlife Refuge) was built by the Spanish in 1882, is still operational. The lighthouse can be seen from the crescent of La Playuela beach, one of the best on the island, and visitors say the short hike to the lighthouse is more than compensated by the great clifftop views.

Mosquito Bay is popular in the evenings, but the island of Vieques' daytime beachcombers like the chalky sands and serene vantage point of southwestern Sun Bay. It's also the only beach on Vieques with public facilities: The approximately 2-mile beach has lifeguards, showers, bathrooms and a small area to purchase food. Plus, the town of Esperanza (and its restaurants and bars) is just a short walk away.

While San Juan's beaches have a distinctly urban vibe, travelers appreciate Sun Bay's comparative seclusion. Reviewers said there's plenty of room to spread out along the beach and it is relatively uncrowded, save for a herd of wild horses. The on-site amenities were also a bonus. In addition, beachgoers say Sun Bay a great family beach; the waves are calm, too. If you're an avid snorkeler, however, you may want to skip these waters as there's not much marine life to see here.

Aricebo is best known for its incredible observatory, but the north coast town has an interesting attraction below the earth, too. The Cueva del Indio is a natural cavern used by indigenous Taino people who left behind a series of paintings on the cave walls. The artwork is estimated to have been made sometime between 1200 and 1500.

Located on the Caribbean coast, the cave entrance is surrounded by dramatic cliffs and arches (the Siete Arcos), one of which is said to resemble the face of an ancient Taino man. In addition to walking through the cave, visitors can explore the cliffs and beach. The caves have appeared as a location for several movies and TV shows, such as the miniseries "Treasure Island" (2012).

The El Yunque National Forest, or simply El Yunque, is the only tropical rainforest in the U.S. National Forest System. It's also a particular favorite for vacationers who like to hike, but even if nature really isn't your thing, travelers urge you to make the trip about 30 miles east of San Juan.

Remember to wear layers that can get wet (the highest elevations can receive up to 200 inches of rainfall annually) and pack a water-resistant camera to capture some of the area's splendor. In the evenings, Puerto Rico's tiny coquí tree frogs begin their unmistakable serenade.

Spanning 27 acres, Castillo San Cristóbal was built to protect Old San Juan from land attacks. It doesn't receive as many visitors or as much adoration as its sister fortification, El Morro, but visitors are typically just as amazed by the majesty and significant history of the site. Allow several hours to visit both sites.

The forts' stellar shoreline views (not to mention the occasional iguana) draw travelers to the sprawling site. Though the fort tends to draw crowds (especially cruise ship passengers), recent visitors said that due to the sheer size of the complex touring San Cristóbal never feels cramped.

Shoppers should come to Old San Juan prepared to let go of a few dollars. The city's Calle del Cristo is a haven of restaurants, art galleries and boutiques. In addition to popular stores, those walking the street can discover local crafts and artisan shops.

If you're looking to skip shopping altogether, Calle del Cristo is still a worthwhile spot to get a feel for the beauty of Old San Juan. Past travelers routinely praised the churches and centuries-old colonial residences and commercial buildings that line the cobblestone streets.

The Camuy River flows through the third largest cave system in the world — so extensive, in fact, that it underlies parts of three towns: Camuy, Hatillo, and Lares. Accessible via the main entrance in Camuy, the small fraction of the caves open to the public can be explored on guided walking tours offered by the Puerto Rico Department of Natural and Environmental Resources, which manages the nearly 300-acre Camuy River Cave Park. Highlights of the tour include the largest stalagmite in Puerto Rico, glimpses of the underground river (and maybe some bats), and a 450-foot deep sinkhole that allows light from the surface to penetrate the cave.

Daily visitors are limited at the cave, so make reservations in advance; day-of tickets are limited. A number of visitors complained about being turned away from the cave because tours were at full capacity. Also, while many praised the beauty of the caves, others noted that the experience requires a great deal of walking, including up some steep hills. Finally, note that the Camuy River Cave Park may be a bit more rugged than some other "show caves" you may have visited. That said, make sure you wear closed-toed shoes.

Located in the bustling Santurce neighborhood of San Juan, the Museo de Arte de Puerto Rico houses more than 1,000 works of art created by Puerto Ricans. The collection showcases pieces that date back to the 1600s and includes sculptures, photographs, paintings, drawings and more. The 24 exhibition galleries are housed across two wings. The west wing is a neoclassical building designed in the 1920s, while the east wing is a modern structure designed by Puerto Rican architects. The east wing also features a stained-glass piece by Eric Tabales called Taíno Sun Rising.

Visitors rave about the museum and say that its exhibits helped them better understand the island's history and culture, with an impressive collection despite its relatively compact size.

If you're staying in San Juan and want to stretch on the sands, you won't need to venture farther than Condado Beach. For many sun-lovers, that's just fine. Condado is framed by a string of high-rise hotels and resort complexes, plus it's ground zero for water sports and beach bars. Families, however, sometimes forego these sands for one of the government-run beaches, or balnearios — notably Playita del Condado — because Condado beach's tide is often too strong for young swimmers.

According to past travelers, you won't be disappointed with Condado, as long as you recognize it's not a remote strip of sand, but rather a beach that sits alongside a bustling city. But its proximity to so many hotels and resorts makes it all the more tourist-friendly.

Located near the Isla Verde resort district in the metro area, lengthy Carolina Beach is a popular public beach among both visitors and locals. Families especially love its white sand, warm water, the on-duty lifeguard and on-site paramedics. What they're not so thrilled with are the crowds. The beach tends to get busy during the weekends, but you can avoid crowds to some extent by visiting during the week.                                                         

There are plenty of vendors nearby selling food and renting water sports equipment. The beach has a volleyball court and a playground for children. It also has a team dedicated to helping wheelchair users, though this service is available Monday through Friday only and must be requested in advance. Another minor drawback is that Carolina Beach's proximity to the airport means you may hear a bit of loud noise from airplanes overhead.

The Reserva Natural Cayos de la Cordillera is a national park that protects the Cordillera Cays, a series of small, uninhabited islands off the east coast of Puerto Rico. Cayo Icacos, aka Icacos Island, is one of the most popular islands thanks to its location just a mile and a half off the mainland coast and its exceptional beaches.

Most visitors come to swim or snorkel for the day — overnight visits are prohibited — and the island's location close to Fajardo makes access easy. For a fee of about $60, water taxis take visitors from Fajardo's Las Croabas neighborhood on the short trip over to Cayo Icacos, making multiple round trips daily from early morning to late afternoon. The island is also a popular stop for charter catamarans doing snorkeling trips. The latter typically supply all you'll need for a fun day on Cayo Icacos, but if you go the water taxi route be sure to bring cash for payment as well as beach necessities (blankets, sunscreen, water and more) since there are no facilities on the island – and that includes restrooms.

Despite its name, you won't need to worry about sinking ships at this beach in Aguadilla. Snorkelers regularly trek to Crash Boat Beach for its clear waters and multitude of fish. The beach and its pier are also beloved by sunbathers, fishermen, volleyball players, scuba divers and daredevils who love to jump into the water from the pier. After a day in the sun, stop by one of the area's many food kiosks to refuel or take a short drive to one of Aguadilla's restaurants.

It's no wonder this western beach is one of Aguadilla's most popular spots for travelers of all ages. Repeat visitors said the beach is smaller after Hurricane Maria, but tourists loved the beach's turquoise waters and ample activities. The near-constant crowds don't seem to bother many travelers, but if you're looking for a quiet environment this may not be the beach for you.

The resort beaches in Condado and Isla Verde are beautiful, but if you tire of the same old scenery, take a 30-mile drive east from San Juan along Route 3 to Luquillo Beach. Families flock to this beach for its reef-protected calm waves, and you'll also see a lot of day-trippers fresh from a jaunt in the nearby El Yunque National Rainforest.

Luquillo Beach isn't usually crowded, but some visitors say cleanliness can be an issue, both on the beach and in the changing rooms and bathrooms. The natural beauty, however, cannot be denied.

Puerto Rico's second oldest city is a miniature Old San Juan in the sense that it has street after colorful street of historic colonial-era buildings dating back to the 16th century. Highlights of the historic district include the Porta Coeli, a convent and church dating to 1609 that's now a museum of religious art — one of many art and history museums in the city — and the Iglesia San Germán de Auxerre, consecrated in 1688. The Museo de Arte Religioso Porta Coeli is open Wednesday to Sunday from 8:30 a.m. to 4 p.m.

Because it's located in the mountains and not on the coast, San Germán sometimes gets overlooked by visitors seeking fun in Puerto Rico's Caribbean sun. But the city once rivaled San Juan in importance as the seat of government for the western half of the island. Visitors can experience local culture at the Fiestas Patronales de San German Auxerre, a July festival celebrating the city's patron saint.

The Arecibo Observatory has a rich history. Scientists used the site's massive telescope to collect data about Earth's atmosphere, the solar system's planets, comets and more since its debut in the 1960s. Though Puerto Rico may seem like an odd place for this important device, it was the perfect location. Situated near the equator, the telescope was in the ideal spot not only to study the Earth's ionosphere (its original purpose) but also to study planets. In addition, Puerto Rico could accommodate the space needed for the telescope's reflecting mirror: The dish is 1,000 feet in diameter and 167 feet deep.

In 2020, cables holding the central platform broke and the platform collapsed into the dish, damaging the dish. In 2022, the National Science Foundation announced it plans to open a STEM research facility on-site but funding would not include rebuilding the telescope.

Set on a hill overlooking Ponce's historic district, the former home of rum baron Don Juan Eugenio Serrallés houses a museum focusing on the sugar industry and rum production. Additionally, because the city of Ponce purchased the mansion with most of its furnishings, visitors get a glimpse of life in a Puerto Rican estate home in the 1930s.

Built in Spanish Moroccan style and listed on the National Register of Historic Places, the Serrallés mansion presides over a 2.5-acre property with formal gardens and an oblong pool. The museum complex also includes a Japanese garden and the Cruceta del Vigía, a 100-foot-tall hilltop crucifix with a horizontal sky bridge served by elevators offering scenic vistas of Ponce.

Afro-Caribbean culture and cuisine draw visitors to Piñones, a small community within the town of Loiza. Settled by formerly enslaved people from the African Yoruba tribe in the 16th century, Loiza is famous for its Festival of St. James, with parades featuring dancers wearing traditional vejigantes masks made from coconuts. But even if you can't make it in July, Piñones makes a great lunch stop on the way to El Yunque, Loquillo or Fajardo. Visitors come to sample frituras like green banana and taro root fritters, seafood pancakes called bacalaítos and other local food at hundreds of food stands in the seaside community.

Piñones isn't just about food: it's a center for a cherished part of Puerto Rican culture called chinchorreo, gathering where friends and family meet for food, drink and dancing. Loiza lacks the big resorts that are typical elsewhere in this part of Puerto Rico, and it's no accident: locals are fiercely protective of their culture and low-key community life.

U.S. News Insider Tip: If you can't make it to Guavate but want Puerto Rico's famous roast pork, head to Naranjito or Trujillo Alto, respectively located southwest and southeast of San Juan. Both are less than 25 miles from San Juan. – Robert Curley

For a deep dive into Puerto Rican culture and cuisine, follow la Ruta de Lechón (the "Pork Highway") into the mountains to the barrio of Guavate (in Cayey), home to a string of lechoneras serving roast pork right off the spit with crispy skin and juicy meat. The communal feast is accompanied by live music; cold beer; sides of mofongo, rice and pigeon peas; and other traditional food.

An admission fee of just $5 gains you entry to what has been described as the most important archeological site focusing on the Taíno people in the Caribbean. The Caguana Indigenous Ceremonial Park is located in the mountain town of Utuado and has a small museum, with visitors also welcome to walk around the excavated remains of stone monoliths, plazas, and ceremonial ball courts, and to view petroglyphs dating to as early as the 13th century. The park also features recreated bohios, thatched-roof homes typical of those built by the Taínos.

The Caguana ball courts, where the traditional game of batey was played, have been designated a National Historic Landmark. The game, played with a rubber ball, was similar to soccer in that all parts of the body other than the hands could be used. Games were also culturally significant in that the games helped Taínos resolve disputes and make important decisions.

The town of Orocovis in Puerto Rico's central mountains is home to this high-energy adventure park, located about 40 miles inland from San Juan. Attractions include multiple zip lines, the roughly mile-long Beast (a zip line that attaches you to a harness so you can fly like Superman) and the Monster, a 1.5-mile zip line. High-altitude tours feature multiple zip lines plus crossing suspension bridges.

The park's ToroBikes operate on the longest cable bike system on earth, more than 1,000 feet long. It's just like it sounds: you pedal a bike across a cable suspended in the air. Other attractions include climbing walls and the ToroRoller, a cross between a zip line and a rollercoaster where visitors are suspended from an overhead track.