One of seven pilgrimage basilicas in the world, this church was founded in 432 AD and is where the famous architect Bernini is buried.

The Basilica de la Sagrada Familia is a church devoted to the Holy Family. One of Antoni Gaudi’s most famous works, the church is perhaps best known for still being under construction since 1882—with works funded purely by donations. Take a lift to the top of the towers for a panoramic view of the city and marvel at the ornate architecture. The nativity facade and crypt have also been awarded UNESCO World Heritage Status. Skip the line with a pre-booked tour with tower access, or combine your visit with another of Gaudi's work, Parc Guell. – Tripadvisor

The majestic ruins of an ancient Greek building, known for its dignified white marble columns and perfect sense of proportion.

The Palau, an icon of modernist architecture in downtown Barcelona The Palau de la Música Catalana is one of the most representative monuments of the city and It is one of the most recommended tourist attractions of Barcelona. Built between 1905 and 1908 by the great architect Lluis Domènech i Montaner, the Palau de la Música Catalana is an architectural jewel of Catalonia and essential part of any visit to the city, as any of the most fascinating Gaudi buildings. This historical building, declared a World Heritage Site by UNESCO in 1997, offers an experience so magical that visitors fall in love with it. From the hand of experienced guides, the wonders of this architectural pearl discovered and visitors into a fantasy world full of details and references to the characteristic nature of modernist architecture. An essential visit in the list of top 10 things to see in Barcelona.

Stroll through the historic center of medieval Barcelona and visit some of the city's most important political buildings and gothic architecture.

Dedicated to the seven planetary divinities and featuring an interior of gorgeous marble, the Pantheon is one of the most impressive monuments of Augustan Rome.

This ancient citadel, built in the fifth century B.C., towers over the city and is home to some of the most impressive ancient ruins, buildings, and artifacts. The most famous temple, the Parthenon, was dedicated to the goddess Athena and is considered the peak of Greek art. You can avoid long lines by joining a walking tour of the site. Make sure to wear comfortable shoes and bring sunscreen, as the walk up the hill can be steep and exposed to the sun. For the best experience, visit early in the morning or late in the afternoon to avoid the heat and for fewer crowds. – Tripadvisor

The ancient Flavian Amphitheater was built by the Flavian emperors in 70 C.E. as a gift to the Roman people. As the largest Roman theater ever built, it was designed to house over 50,000 people, and had played host to gladiator games, plays and even public executions. Purchase skip-the-line tickets online to avoid long lines at the door, or join guided tours which allow for special access to restricted areas. While here, you might want to visit the adjacent Palatine Hill and Roman Forum as well. – Tripadvisor

Located at the foot of Palatine Hill, the Forum is surrounded by ruins of Rome's most important government buildings. It's usually visited alongside the famous Colosseum.

A jewel of the La Ribera neighborhood, this is Barcelona's last remaining Catalan Gothic-style church, with majestic naves and beautiful stained glass windows.