Lucerne's central prison was converted into a tourist hotel with a bare minimum of changes.

The largest underground lake in Europe.

A once-thriving hotel in the Swiss Alps couldn't compete with climate change.

Home of the Large Hadron Collider and the birthplace of the World Wide Web.

This hidden fortress has been coined the "City of Ghosts."

This park was designated by UNESCO as an Endangered World Heritage site.

A 19th-century architectural masterpiece with ties to Gustave Eiffel.

A tree seems to grow from the ocean floor on this strange strip of sand slowly being overtaken by the sea.

These homes carved into the mountains seem to defy the laws of nature.

The central mosque of this Mali town is entirely built from mud.

An abandoned village, frozen in time by the threat of a landslide.

This sign marks the entrance to a tiny proto-state within the small country of Moldova.

There is a mouldering Jewish cemetery hidden away in the capital of Moldova.

The largest wine cellar in the world is a 150-mile network of underground caves near the capital of Moldova.

A swath of France so devastated by war it is still forbidden to go there.

Once a bustling fishing port, this semi-ghost town is now more than 90 miles away from the shore.

Ancient barriers wrap around what was once an important stop along the Silk Road.

The Avenue of Mausolea is a series of grand palatial tombs.

Light still pours into the ruins of this ancient Islamic observatory.

One of the most horrible legacies of the Cold War is a site where the Soviet Union tested nuclear bombs on civilians.

Rusting ships sit in a desert where a sea used to be.

This dark, damp, perilous tunnel is the only passage from north to south Tajikistan.

Located along Lysaya Mountain, this monastery is home to the largest statue of Buddha in Russia.

The last stop in southeast Russia.