The former Nazi concentration camp stands as a museum to remember this dark chapter in European history.

An underground city of salt.

An extensive collection of reliquaries containing the bones of saints housed in the largest Catholic church in Venice.

An important Mayan religious and trading center dating back to 200 BC.

A floating cat sanctuary on an Amsterdam canal.

Hamburg's first legal sex work is relegated to a gated street that still does not allow pedestrian women.

Once the tallest building in the world, this abandoned church is now a monument to the destruction of WWII.

This once-forgotten oasis in the middle of Lisbon was first created over a century ago quite by accident.

A little sculpture with a large wardrobe.

This is the oldest Roman-made bridge in the city still existing in its original state.

The celebrated eyesore created by starry-eyed sweethearts.

A Bronze age settlement on the Greek island of Santorini might have been the inspiration for Plato's Atlantis.

A former factory serves as a shrine to the industry that sustained Santorini for decades.

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

The ruins of an ancient Roman tomb hidden in the basement of a trendy clothing store.

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

This statue was given to France by the United States to commemorate the centennial of the French Revolution.

The giant statue and its model solar system honor the native Pole who declared that the Earth revolves around the Sun.

The Polish capital has had a deep connection to its guardian mermaid for almost a millennium now.

St. Mary's features one of the most spectacularly decorated cathedral interiors in all of Europe.

Famously misunderstood wonder of the ancient world

This hidden collection of everyday objects illustrates life within communist Poland.

A program of Communist glamour in post-Stalin Poland is preserved in this colorful museum.

There must be a pun in this haystack somewhere...