A sixth-century Byzantine cistern hidden below a modern carpet store.

The ruins of an abandoned medieval city where the last Byzantine emperor was crowned.

The monumental home of Prussia’s eccentric "Cannon King."

The second-largest Jewish temple in Bulgaria was deserted after World War II, seized by the communist government and then abandoned again.

This monolithic slab of art metal crowns a German slag heap.

This fairytale castle was built as a show of power but was nearly torn down thanks to its history of torture.

This historic stone bridge has an entire neighborhood clinging to its sides.

This futuristic German television spire is actually the world's largest digital clock.

The Bauhaus-style former industrial complex is considered the world's most beautiful coal mine.

Most prolific publishing house in the 1600s open to the public.