This colorful but controversial ceiling has been likened to a 21st-century Sistine Chapel.

Large Hadron Collider and the Birthplace of World Wide Web.

An early 20th-century bullring converted into a modern shopping center.

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

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

This cemetery features modernist statues as strange as its name.

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

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

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

Visitors to this Belgium graveyard are greeted by the grieving stone parents of the young men lost to war.

The site where one of the most famous poems of World War I was composed is preserved to honor the legacy of the work.

In an area where the remnants of WWI are discovered on a regular basis this preserved frontline trench may be the most amazing.

A rare example of World War I trenches from the British front.

This memorial museum chronicles the apocalyptic destruction of the First World War.

Amsterdam's narrowest house facade is a monument to 17th-century tax evasion.

The last of Amsterdam's original sea level markers remaining in place.

This bird-loving brewery is situated in an old municipal bathhouse, nestled beside a 300-year-old windmill.

Amsterdam's former hotspot for public executions and dissections.

A public urinal so pretty, it was declared a national monument.

Established in 1638 to battle the Black Death, Hortus Botanicus Amsterdam is a treasure trove of rare flora.

This chimerical bridge/tunnel appears to dead end right into the sea.

This poignant sculpture of a gnarled weapon is a symbol of non-violence.

Swedish skyscraper with a 90° twist.

Climb to the top of its spiral spire for spectacular views of Copenhagen.