This domed temple was built in a hidden cave mouth as a refuge for sinners seeking absolution.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

The most visited, and possibly most controversial, museum in Germany.

Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

Where commuters walk through remnants of an ancient Greek necropolis.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

The water-powered carriages are long gone, but for over a century this funicular railway has been the fastest route to the highest point in Paris.

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

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

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

A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.

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

Taking the subway here means doing so over a bridge located in the middle of an estuary.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

Legend says if you stick your thumb in the hole and it gets wet your wish will be granted.

Built in 1512, the oldest cathedral in the Americas.

After Christopher Columbus died, his son built a fancy house to rule from.

A Dutch clog company in the town of Zaandam loves the wooden shoes so much it made a museum for them.

This old KLM airplane cut into three parts was transformed into an eclectic airport gift shop.

Some 80,000 Delft Blue tiles line the inside of this Amsterdam walkway.

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

A hidden church in a hidden courtyard tells the story of the Miracle of Amsterdam.

A misnamed well, with a deep dark past.