Designed by Gustave Eiffel before his famed tower.

One of Antoni Gaudí’s earliest buildings, built between 1886 and 1890 for the industrialist Eusebi Güell.

Step inside the first house designed by Catalan architect Antoni Gaudí, considered to be one of the first Art Nouveau buildings.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

The largest Art Nouveau complex in the world is a Barcelona hospital with a 600-year-long history.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

This extinct volcano rises above Edinburgh and is special for its panoramic views over the city.

This uniquely shaped rock formation is one of Scotland's most iconic mountains and gives spectacular views in all directions.

The 18th-century inspiration behind Harry Potter's Sorting Hat.

A ceramic postbox where visitors can post original poems and creative messages.

Twenty carved heads in Glasgow take a comical, modern twist to the medieval apotropaic, avenger of evil.

This astronomically-aligned stone circle was the first of its kind to be built in Great Britain after a 3,000-year hiatus.

An 18th-century religious argument etched into stone.

A small collection of objects of a bygone era hide in plain view.

An underground city beneath Krakow's postwar socialist utopia.

The ornate structure is part of a building boasting more marble than the Vatican.

At first glance, this area seems like just another city park, but the lush landscape hides a dark past.

The somber sculptures commemorating Irish Famine on the river Liffey in Dublin.

One of Ireland's most infamous prisons for rebels including men, women and children.

The enchanting archway is the only surviving portal into Dublin's lost medieval wall.

An Irish church where an 800-year-old mummy is reaching out of his coffin as if to shake hands.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

This tin chapel was built by POW's during World War II and is painted to look like something much more grand.

Memorial to the Titanic engineers that died working to hold back the sea.