Accessible only at low tide, the deserted island is dotted with World War II ruins.

The U.K.'s first underground railway line is now a lively thoroughfare for runners and cyclists.

A shiny sculpture celebrating the mighty mollusk.

This abandoned five-star hotel is now a five-star urban exploration destination.

This fairy-tale, neo-Gothic church in the Azores is a world of magical realism.

A Victorian park cemetery, standing on the site of what was once the Great North Wood.

An artistic tribute to the famous singer, just around the corner from where he was born.

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

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

Construction of Barcelona’s iconic (but controversial) church was finally completed in 2026—a century after the death of its architect.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

Once the home of a hermetic monk, this cave now houses a small church.

It houses the remains of a 17th-century version of the Titanic.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

The old observatory in Copenhagen has a spiral corridor used as a racetrack.

Danish tourist destination well known for open stalls where vendors sell marijuana on the street.

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

A large grotto built in the 16th century amidst Florence's famous Boboli gardens.

This wrecked airplane has been sitting on a black sand beach since the 1970s.

A sulfuric martian landscape that looks far better than it smells.

This hobbit-y little hot spring may be the oldest spring used by humans in all of Iceland.

This eye-popping Icelandic crater lake is surrounded by red volcanic rock.

This elegant arc of a waterfall marks a religious turning point.

Iceland's largest lagoon is home to stunning multi-colored icebergs.