This iconic arching iron bridge straddles the Douro River, connecting Porto to Vila Nova de Gaia. Though Porto is known for having quite a few bridges, the Dom Luís I Bridge is especially renowned because it was designed by a student of Gustave Eiffel, the mastermind behind the Eiffel Tower in Paris. Plus, at the time of its completion in 1886, this bridge was the longest iron arch in the world. The bridge accommodates cars on its lower level and Porto's metro on its upper level; pedestrians can walk along the bridge on both levels. Stroll along the upper deck of the bridge and you'll be rewarded with spectacular views of the edifices built into the hillside cliffs that line the river.

Admiring the bridge's composition and the views it offers is something all visitors to Porto must do, according to recent travelers. "This bridge has got to be one of the most amazing pieces of architecture," swooned one TripAdvisor user. "Be sure to walk both top and bottom levels if you can, views are excellent!" A visit here would pair well with a stop at some of Porto's nearby wineries across the bridge in Vila Nova de Gaia. Another option would be to hop on a Douro River cruise or boat tour, which would allow you to see all six bridges in one go.

Perched on a hilltop standing watch over the city, the Porto Cathedral (known as the Sé) was originally built between the 12th and 13th centuries, and features a variety of architectural styles, including Romanesque, baroque and gothic. The fortress-like church is the largest in the city and one of Porto's oldest monuments; it's flanked by twin towers and has a rather plain stone facade. But inside the Sé you'll find a beautiful stained-glass rose window, a collection of centuries-old sculptures and a silver altarpiece that was once used as the bishop's study. Meanwhile, the cloister boasts cobalt and white ceramic tiles that depict different scenes from religious history. Most travelers say visiting the church and cloister is absolutely worth an hour or two, noting that the exterior is remarkable but the interior is exquisite.

This particular attraction is also popular with visitors thanks to its vantage point. You can meander along the terrace outside the church and admire the views (and take photos) of Porto's terra cotta-colored rooftops below.

The Crystal Palace Gardens boast green shrubbery, winding walkways, bright flora and bubbling fountains. Bring your camera along because you'll find plenty of photo opportunities here: Everything from the flower varieties to the expansive views of the Douro River beckons for your attention. (And if you're lucky, you may even catch a glimpse of the peacocks that roam the gardens.) The park's name comes from the Crystal Palace that once stood here, though it was torn down in 1956 and replaced with a domed pavilion that houses a sporting arena and a multi-purpose events center. Recent visitors say the pavilion is not worth a visit, but the park should be experienced.

The best way to get to the Crystal Palace Gardens is via metro to the Aliados stop on the D (yellow) line or the Carolina Michaelis stop, which services the A, B, C, E and F (blue, red, green, purple and orange) lines. You could also pick up the No. 200 bus toward Bolhão or No. 207 bus toward Campanha along Rua do Campo Alegre and get off at the Palacio stop; the 12M bus also services the Palacio stop on its way from Porto to Vila Nova de Gaia. The gardens are open daily until dark and are free to explore.

Porto's main thoroughfare, Avenida dos Aliados, features a smattering of cafes, hotels, banks and boutiques all housed in architecturally impressive buildings. Located in the heart of Porto, just southeast of the famous Bolhão Market, this wide avenue is named to honor the Allies of World War I. Most of the buildings showcase intricate design in their cupolas and cornices. Points of interests include Porto's granite and marble town hall (which sits at the northern end of Avenida dos Aliados), General Humberto Delgado Square (marked by a few trees and situated in the center of the avenue) and Liberdade Square (which serves as the anchor to the avenue and is marked by a statue of King Pedro IV riding a horse). The central portion of the boulevard often hosts artists, street performers and festivals.

The best way to enjoy Avenida dos Aliados is by strolling along the street to revel in its buzzing atmosphere, and pick a cozy spot to order some cafe (coffee). "The architecture that surrounds this plaza allows for some excellent photographs — go on a sunny day!" said one TripAdvisor user. "At the north end, small chairs … allow for some lounging and people-watching."

A visit to Porto wouldn't be complete without a stop to sample the city's most notable export — port wine. You'll find dozens of wine cellars scattered throughout Porto, and there's even a Port Wine Museum dedicated to teaching the history of the port wine trade and production development. But if you're more interested in imbibing, head to one (or several) of Porto's top wineries.

Sogrape Vinhos owns Ferreria, Sandeman and Offley cellars, and all three northern Vila Nova de Gaia venues are within walking distance of one another. Start at Ferreira, the westernmost winery, which was built in 1751 and has long played an important role in Porto's winemaking history thanks to its family of notable winemakers. Head east along Avenida Ramos Pinto and you'll happen upon your next stop, Sandeman Porto Cellars. Sandeman is the most recognizable wine cellars in the region, situated along the picturesque banks of the Douro River and boasting massive white lettering spelling out the winery's name. This winery also features various paintings, photographs, antique bottles and other trinkets that outline the history of the Sandeman brand. South of Sandeman you'll find Offley Cellars; built in 1737, the Offley cellar is the eldest of those owned by the Sogrape Vinhos brand. A singular visit to tour and sample wines at one of the Sogrape Vinhos cellars costs anywhere from €3 to €35 EUR (about $4 to $50 USD) depending on what type of experience you seek. (Some packages include tastings with a wider variety of wines, some boast a more intimate experience and some include tapas samplings as well.) However, if you're hoping to do a wine tour and basic tasting at all three cellars, you can do so for €10 EUR (around $14 USD).

Built on the former site of a Benedictine monastery, the São Bento Railway Station was inaugurated in 1916; today, trains pass through here carrying travelers between Porto and many of its northern suburbs. But you likely won't be visiting here to hop a train anywhere. What's notable about this landmark is its 20,000-some painted blue and white tile panels (known as azulejos) that highlight the history of Portugal. Portuguese artist Jorge Colaço is the mastermind behind this azulejo piece; its tiles were mounted over the course of a decade — from 1905 to 1916. Some of the most impressive scenes include King João I and Queen Philippa standing near the city's cathedral in 1387 and a depiction of the Battle of Arcos de Valdevez.

While it may seem unusual to see such detailed artwork in a train station, one TripAdvisor user goes as far to say a visit to Porto just isn't complete until you step inside. "The architecture and beautifully painted tiles speak to the heavy religious influences in Porto. Take your time and enjoy … the clock and the intricate steel structure once inside too."

Scents of sweet fruit, freshly baked bread and aromatic cheeses greet visitors as soon as they enter the Mercado do Bolhão. This open-air market is reminiscent of many you'll find in Europe, with vendors hawking a variety of fresh goods and homemade wares at very affordable prices. The market, which dates back to 1850, is housed behind a neoclassical facade in a two-story building in the heart of Porto. While some recent visitors say the building is in need of some renovations, they note the bustling energy of the market and delectable treats make up for the aging facility.

Bolhão Market is open Monday through Friday from 7 a.m. to 5 p.m., and on Saturdays from 7 a.m. to 1 p.m. Entry is free, but you should bring along some cash to spend on the fresh food that may tickle your fancy. You can reach the market by taking metro line A, B, C, E or F (blue, red, green, purple or orange) to the Bolhão stop. For more information, visit the Porto tourism board website.

Porto's location along Portugal's northwestern coast grants the city access to some prime beachfront. If you find yourself experiencing a sunny day, visiting Portugal's northwest coast is a great way to pass the time. In Foz, located east of the city center along Avenida do Brasil, you'll find a handful of small beaches, like Praia do Molhe and Praia de Gondarém. Though picturesque, the terrain just offshore is a little rocky, so swimming isn't advised. But you can still bring a towel to lie on the sand, soak up the sun and dip your feet in the cool Atlantic for a little refreshment. Speaking of refreshment, this area of Porto is also packed with plenty of beachfront bars, restaurants and cafes — it's quite a popular place to enjoy the outdoors both day and night.

Meanwhile in the town just south of the Porto city center, Vila Nova de Gaia, you'll happen upon beaches with soft white sand and conditions more suitable for swimming. The beaches of Vila Nova de Gaia are known for their impeccable water quality, environmental awareness and safety — awarded and recognized with blue flags — making them some of the most impressive in Portugal. Madalena, Lavadores, Salgueiros and Miramar are some examples of beaches you can travel to from Porto. Both active types and those looking for a little R&R will find a day at one of these beaches enjoyable: The shorelines here feature amenities like volleyball nets, bike paths and shaded cabanas.

Everyone knows the old adage, "don't judge a book by its cover" — the notion couldn't be truer in the case of the Igreja de São Francisco. This church looks rather plain on the outside, sporting a stone facade with elements of gothic and baroque styles, but step inside and you'll be greeted with gold: lots and lots of it. An abundance of gilt wood carvings (reportedly more than 800 pounds of gold) make up the columns, vaulted ceilings and walls of this UNESCO World Heritage Site church, which started to take shape in 1245. A traveler favorite amid the luster is the Tree of Jesse, a massive family tree sculpture that traces Christ's genealogy and dates back to 1718.

The Igreja de São Francisco is located right next to the Palácio da Bolsa in the heart of Porto; it's easily accessible via the São Bento metro stop on the D (yellow) line. The church is open daily from 9 a.m. to 5:30 p.m. November through February; from 9 a.m. to 7 p.m. March through October; and from 9 a.m. to 8 p.m. July through September. Admission costs €3.50 EUR for adults (about $4.75 USD) and €2.50 EUR for children (about $3.50 USD). Services are no longer held here regularly, though the church does host classical music concerts and some religious ceremonies like weddings and baptisms, so leave some flexibility in your schedule to come back later, if necessary.

A bookstore may not seem like one of the most necessary things to see in a new city, but when it's consistently named one of the world's most beautiful, it's worth a look. Situated among the cafes and shops along Rua das Carmelitas in downtown Porto, Livraria Lello easily stands out with its chalk white, neo-gothic facade featuring intricate carvings and two painted ladies (representing science and art). Step inside and you'll be even more impressed. The bookstore's interior is adorned with rich wooden paneling and colorful stained glass windows, and boasts a regal ruby red staircase. As for the books, you can peruse an assortment of Portuguese fiction and non-fiction works, as well as a selection of books in English and French.

Travelers are often impressed by Livraria Lello's allure and say visitors should take a peek inside. Most visitors commend the charming atmosphere and exceptional artistry evident in the Livraria Lello's architecture, but also warn that photos are not allowed. You can purchase professional photos on site for around €5 EUR (about $7 USD), or stay awhile to grab a coffee, take in this bookstore's beauty and commit the image to memory.

One of the most-visited sites in Porto, the Palácio da Bolsa is renowned for its exquisite neoclassical facade and ornate gilded Arabian Hall. This massive building — located in the historic center of Porto — once acted as the city's stock exchange, wooing European bankers and investors alike. Today, you can tour the interior with a guide and see the glass-domed Pátio das Nações (Hall of Nations) and the magnificently golden Salão Árabe (Arabian Hall, which was designed to mimic the Alhambra Palace in Granada, Spain), as well as the numerous portraits that adorn the walls.

Travel experts and publications consistently laud the Palácio da Bolsa as a must-see stop in Porto, but recent visitors offer mixed reviews. Some travelers say the tour price is a little high and not being able to take photos is discouraging. But others note the sheer splendor of the interior and learning the history behind the building is worth the price.

The Fundação de Serralves comprises a park, a villa and a contemporary art museum all set on nearly 45 acres of land in western Porto. Billed as a cultural institution, the foundation aims to "raise the general public's awareness concerning contemporary art and the environment." The villa and park were the first to open (in the 1930s); the villa is often touted by architecture experts and historians as the most noteworthy example of an art deco building in Portugal and it was declared a national monument in 2012. Inside, the villa is laid out like a private residence (as it was originally such) and hosts temporary art exhibits throughout the year. Situated on one of the highest points of the complex, the villa overlooks the park, which features lush gardens, exotic plants, winding pathways and even a farm. Permanent sculptures pepper the premises as well. Meanwhile, the Serralves Museum opened in 1999 and boasts 14 exhibition galleries across three floors. Today, the museum features rotating art exhibits, music and dance performances, and educational programs.

Although it's a bit removed from other top attractions around Porto, the Fundação de Serralves is well worth a visit for its beautiful gardens and interesting art, recent travelers say. Also, if you happen to be visiting in late May or early June, you can take part in the museum's annual Serralves em Festa festival, which offers a plethora of free contemporary art and cultural events and performances.

Founded in 1833, the Museu Nacional de Soares dos Reis was Portugal's first public art museum. Art lovers will appreciate the expansive collection housed here, as well as the ornate building itself. Occupying a former royal residence, the museum features much of the work of its namesake, António Soares dos Reis, including his famous marble sculpture, "O Desterrado" ("The Exiled"). Inside the museum you'll find a vast selection of Portuguese paintings and sculptures from the 16th to 20th centuries created by a variety of artists. The museum also features furniture, jewelry, fabric work and glassware. Recent visitors noted they were pleasantly surprised at both the beauty of the extensive collections and the regal building, calling the museum "a real gem."

Tickets for admission to the National Museum Soares dos Reis cost €5 EUR (about $7 USD) for adults and €2.50 EUR (about $3.50 USD) for children, seniors and Porto Card holders. The museum is open Tuesdays from 2 to 6 p.m., and Wednesday through Sunday from 10 a.m. to 6 p.m. (Admission on Sundays is free until 2 p.m.) You'll find the museum on Rua D. Manuel II, less than a mile northwest of the Church of Saint Francis and Stock Exchange Palace. The Aliados station on the D (yellow) line is the nearest metro stop; from the metro, it's a little less than a mile walk southwest to reach the museum. For more information on the National Museum Soares dos Reis, visit the facility's website.

While Portugal may not be as well-known for having avid soccer fans as Spain or England, the Portuguese still love their futebol. Porto's home team, F.C. Porto, is one of the country's "Big Three" — the three most successful multi-sports clubs in Portugal — and plays in Dragão Stadium. You can take a tour of the stadium: A guide will escort you to see the presidential box, locker rooms and players' benches. Or, skip the tour and explore the on-site museum, which highlights F.C. Porto's history and showcases trophies like the UEFA Cup and European Super Cup. But if you really want to experience the stadium come alive, get a ticket to a soccer match.

While tickets for games can be pricey, most travelers say it's well worth the cost to see the passionate fans and talented players. "This stadium is full of magic. The design is magnificent and the atmosphere is spectacular," said one TripAdvisor user. "Everybody should go there."