A stunning architectural marvel often compared to Sydney's opera house, the Elbphilharmonie is a concert hall and performance space designed by the Pritzker Architecture Prize-winning Swiss architecture firm Herzog & de Meuron. As soon as it opened in 2016, it became an instant architectural icon thanks to its wave-like rooftop and glass façade. Luckily, you don't need tickets to a show to enjoy the striking space.

A public viewing platform is open to everyone and offers breathtaking, 360-degree views of the city and the harbor – a particular highlight for recent visitors. While admission to the viewing plaza is free, you do need a ticket to enter. Advance booking is available and recommended by recent visitors, though a booking fee of 2 euros (or about $2.25) applies. Reviewers also recommended taking a harbor cruise to admire the building from the water.

The Alter Elbtunnel (also called the Old Elbe Tunnel, St. Pauli Elbe Tunnel) is a pedestrian, bike and motorist tunnel (though cars are not permitted), which travels underneath the River Elbe. It connects central Hamburg to the southern side of the river. Opened in 1911, the tunnel was built to serve the port and shipyard workers as a connecting route between the Landungsbrücken and Steinwerder piers. It became a tourist attraction when the "new" Elbe tunnel opened in the 1970s. It has been undergoing renovation for the past several years.

While walking through the quarter-mile-long tunnel, take time to look at the tile reliefs that line the walls, which portray starfish, dolphins and other creatures. Past travelers enjoyed the experience of walking beneath the river and taking in the great view from the opposing side. Others said it provides an interesting photo opportunity, though there is little else to do.

Planten un Blomen, which translates as the very imaginative Plants and Flowers, spans over 100 acres and is a favorite among locals and travelers. Referred to as "Hamburg's green lung," it is home to various themed gardens, including a rose garden, Mediterranean terraces and one of the largest Japanese landscaped gardens in Europe. Planten un Blomen offers much more than the eponymous "plants and flowers." There are playgrounds, mini-golf, an ice rink in winter and a roller rink in summer, and even life-size chess games. There are also several cafes and food kiosks.

Many past visitors said the park is a relaxing place to unwind and highly recommend touring the Japanese garden. Others said the park is well-maintained and a worthy stop even in the offseason.

No visit to Hamburg is complete without getting out on the water. The easiest, not to mention one of the least expensive, ways to enjoy Hamburg by water is via a public ferry. Head to the Landungsbrücken piers and hop aboard one of Hamburg's many public transportation options.

One of the most popular ferry trips is aboard the No. 62 toward Finkenwerder island, which takes 30 minutes and allows you to see some of the city's most important waterfront sights. You can also hop on a guided tour, many of which also operate from the piers at Landungsbrücken. You'll enjoy an overview of the industrial docks, the historic Speicherstadt warehouses and modern architecture highlights such as HafenCity Hamburg and the Elbphilharmonie. Rainer Abicht Elbreederei and Barkassen-Centrale Ehlers GmbH earn high marks from recent tour-goers. You can find more information about available harbor cruises on the city's tourism website.

All-night revelers finish up their partying at the Sunday morning St. Pauli Fischmarkt (Fish Auction Hall and Market) and early morning shoppers get a head start on the day. Not only are there stalls brimming with fresh fish and other goods, there's also steaming hot bratwursts, free-flowing beer and even an energetic band to keep the jovial atmosphere alive. It's also one of those uniquely Hamburg attractions, one which has been an institution since 1703. If you sleep in (or you're just getting to bed after bar hopping), you'll miss out on the Fischmarkt; it's open on early Sunday mornings only.

Recent visitors who knew what they were in for say the scene is fun and festive, while those looking for a traditional market were a bit disappointed. Reviewers described the scene as merry, with many comparing it to Oktoberfest.

Self-described as the world's largest model railway, the more than 10,000-square-foot Miniatur Wunderland takes visitors around the world to admire models of miniature-sized countries and cities, including Southern Germany, Hamburg, USA, Scandinavia, Switzerland and Venice. Across nine different sections are more than 1,000 trains, 130,000 trees and nearly 250,000 figures.

Recent visitors offered rave reviews for Miniatur Wunderland, saying it was appealing to both kids and adults alike. Others were in awe of the attention to detail. However, a few warned that since this is a popular attraction, it can get very crowded. Miniatur Wunderland advises timing your visit in the early morning or late afternoon to avoid the largest crowds.

St. Michael's, Hamburg's largest church, is actually the third church to be built in the same spot and was constructed in 1912. Visitors flock to the landmark church to see its five different organs, its 65-foot altar, its crypt and the amazing views from the nearly 350-foot-high observation deck. The church's 433-foot-tall tower, home to Germany's largest clock bell, is visible from all over the city. In the crypt far below, about 2,000 people have been laid to rest.

Views from the top are not to be missed, according to recent visitors. Others described the church's interior as "ethereal." What's more, travelers were pleased with the affordable admission fee.

The Tierpark Hagenbeck (or Hamburg Zoo) is owned by the Hagenbeck family; Carl Hagenbeck, Jr. (who founded the zoo in 1907) was a wild animal trader and merchant. One of his innovations was to use moats instead of cages to enclose animals, a practice still used to this day. Today, visitors can encounter thousands of animals at the zoo, including one of the largest elephant herds in Europe. Of special note is the four-level Tropical Aquarium, an artificial habitat comprising more than 14,300 animals, including Nile crocodiles and around 13,000 fish. There are also several restaurants, playgrounds for kids, feeding demonstrations and a recreation park, among other attractions.

Recent visitors advised allowing plenty of time to check out all of the exhibits (some said they spent the whole day at the zoo) and said it's a great family-friendly activity. Reviewers were particularly fascinated by the walruses and polar bears. According to travelers, the zoo provides food to feed select animals (donations are encouraged).

Just as compelling and moving as Ellis Island, this museum and ancestral research center conveys the story of European emigration to the United States and elsewhere. The museum occupies the land originally used by the Hamburg-Amerikanische Packetfahrt-Aktien-Gesellschaft (HAPAG) shipping company for the city's Emigration Halls, which were built 120 years ago to accommodate people from all over Europe hoping to sail across the Atlantic. To lessen the likelihood of immigrants being sent back from the United States due to illness or other reasons (at the shipping company's cost), HAPAG offered medical examinations. Millions of people passed through the complex, which at one point included a hospital, a church, a music hall, housing and even hotels.

There are several halls that detail why people were emigrating, their journey across the ocean and what happened when they reached America, with interactive exhibits, displays, photos and artifacts. For an even more immersive experience, consider grabbing a bite to eat at the on-site restaurant Nach Amerika (or "To America"), which serves meals based on recipes used in the canteens of the former Emigration Halls. Visitors can also search complete passenger lists of all the ships that left the harbor in the family research area.

One of Germany's great art museums (and one of its largest in terms of exhibition space), the Hamburger Kunsthalle boasts an extensive collection of paintings and sculptures – both old and new. The permanent collection encompasses art from eight centuries – with some pieces dating back to the Middle Ages. In the modern and contemporary sections, artists like Andy Warhol, Max Beckmann and Bruce Nauman are represented; in the older sections, you'll find works by Rembrandt and Anthony van Dyck, as well as a noted collection of works by German Romantic painters.

The museum is a highlight for many recent visitors, who rave about the excellent collection, especially the representation of German painters. Others were impressed by the building.

The Rathaus (City Hall) is big – bigger than London's immense Buckingham Palace – and according to travelers, it's one of the best sights in Hamburg. Resting on a square, inspired by Venice's Piazza San Marco, the neo-renaissance building's formidable exterior opens into a lavish interior, which is peopled by Hamburg's city council and state government officials. English-language tours take about 45 minutes and wind past the opulent state rooms, a mere fraction of the 647 rooms located on-site.

Recent visitors called the building "beautiful" and recommended taking the tour if you can.

Located in a former warehouse, the International Maritime Museum offers a look at 3,000 years of maritime history across nine floors, with a stunning number of exhibits, artifacts and more, including thousands of model ships – a highlight for many recent visitors. Others were pleasantly surprised with the interesting and informative exhibits. One of its most treasured pieces is a copy of the "Atlantis Majoris" from 1657, the first nautical atlas printed in the Netherlands. Other exhibits include medals and uniforms from navies around the world, displays of commercial and passenger shipping and works by well-known maritime painters. One way to tackle the massive museum is by taking a 60- or 90-minute tour, which is offered in English, and costs 70 euros (about $77) and 80 euros (around $88), respectively. Audio guides are also available for a much smaller cost.

Recent visitors called the museum "fascinating" and said you should be prepared to do a lot of walking throughout its various levels and set aside several hours. However, some reviewers expressed disappointment that a few exhibits did not offer English translations. 

The red brick buildings of the Speicherstadt (Warehouse District) used to shelter the city's imports – coffee, spices, silks – which were carried fresh off the boats in the harbor. In 2015, Speicherstadt became Germany's 40th UNESCO World Heritage Site. Today, this area full of neo-Gothic buildings, mostly constructed between 1883 and the late 1920s that are fun to see on foot. Though there are a few attractions within the area, including Miniatur Wunderland and the International Maritime Museum, it mostly attracts visitors in search of photo ops and a picturesque stroll. Popular photo spots include the Wasserschloss (or "water castle") at the end of Holländischer Birdge and Fleetschlösschen, a former customs booth.

Recent visitors call the area magical and recommend taking a canal tour if you can. A few reviewers said it's worth visiting at night when the area is beautifully illuminated.

Hamburg's Reeperbahn once rivaled Amsterdam's Red Light District for its sex trade, but times have changed (slightly). Located in St. Pauli, the Reeperbahn is a nightlife hub, still notorious for its corridor of sex shops, strip shows and brothels, though there are plenty of other non-X-rated activities and sights, from dive bars to the Beatles monument (the Beatles made their mark in Hamburg). St. Pauli is now almost better-known for its huge live-music scene, with clubs, bars, theaters and music venues. The annual Reeperbahn Festival in September brings in around 25,000 people to hear live music.

Recent Reeperbahn visitors found the area interesting to see, with plenty of music and pubs to check out. Others warned of potential pickpockets.

Head to the Hamburg Planetarium to see everything from children's films to 3D trips through the solar system. The art deco building dates back to 1912 and is considered one of the world's oldest observatories. Visitors can also enjoy concerts and other musical shows in the enormous domed hall. The high-tech planetarium claims it's the most modern planetarium in the world. Previous shows include "Night Flight through the Galaxy," "Laser Zeppelin," and the "Green Planet 3D." After your show, head up to the rooftop terrace for unparalleled city views.

Recent visitors were impressed with the planetarium and highly recommend seeing a show there. Others suggested taking a stroll through the lovely Stadtpark City Park, where the planetarium is located, before or after a show.