The ruins of an ancient mansion sits in front of and underneath a contemporary art gallery.

This abandoned shopping arcade has new life as an art installation.

The ruins of this ancient fortification wall sit in the middle of a quiet, residential intersection.

Spanish architects used seized Muslim gravestones to rebuild parts of the fortress.

These ancient ruins hide in plain sight next to a dessert shop.

Only open for two days a year, this church links ancient Greek and modern Christian celebrations.

According to legend, this cavern holds the passage that Persephone used to travel to and from the underworld.

A spitting ode to a German serial killer.

There are many Byzantine-era churches still standing in Athens, but this is the only one with a 2,500-year-old column rising through its roof.

Böttcherstraße's bells, extolling Nordic virtues and the great conquerors of the world.

A 2,000-year-old computer demonstrates remarkable engineering and astronomical precision.

This small 16th-century church in Athens is almost entirely surrounded by a modern building.

Overlooking the harbor is a beautiful neglected mansion guarded by two Egyptian sphinxes.

The site where hundreds of Greeks were tortured by the Nazi secret police is now a cosmetics store.

This graffitied 19th-century building was a prototype of European industrial architecture.

Makers and sellers of the original and finest York Ghosts.

Elaborate stone houses constructed from the ruins of war.

Terrifically morbid cemetary and site of famous Paracelsus' grave.

Once designed as the entrance to Buckingham Palace, this structure was later relocated and stands as a victory arch.

A martyred saint built a nunnery and school for girls here known as the "Parthenon."

One of Amsterdam's narrowest houses is located right across the canal from its widest.

A naturally mummified 2,000-year-old man.

This intriguing Bronze Age artifact spent centuries hidden within a Welsh faerie hill.

Amsterdam's former hotspot for public executions and dissections.