This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

A whimsical and twisted animatronic monster tour beneath the streets of Berlin.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

An eerie, derelict amusement park in Berlin.

Overlooking the burial ground is a tower designed to prevent thieves from snatching the recently deceased.

A series of three shiny letters mark the boundary of an old refuge for those being pursued by debt collectors.

A poetic monument to the Scottish Parliament.

Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

A six-ton wedding present for the King of the Scots.

The building where Mary, Queen of Scots was said to have bathed in white wine.

This former train tunnel is filled with lines from a poem crafted by Robert Louis Stevenson.

This stately bank building hides a spectacular star-studded ceiling.

The colorful stairs are made with marble from the world's major quarries.

Enter this small nook and you'll be surrounded by 360 degrees of street art.

This early version of the guillotine was used to execute the man responsible for its construction.

The U.K.'s first underground railway line is now a lively thoroughfare for runners and cyclists.

One of Edinburgh's oldest pubs hides a 19th-century skittles alley in the back.

These steps offer a breathtaking view of one of Europe's most besieged fortresses.

Overlooked by many, the two famous Scottish warriors guard the main gate of Edinburgh Castle.

A library where thousands of books explain how to avoid another Great Recession.

A statue in the heart of Edinburgh honors a bear that served in the Polish military during World War II.

A sweet symbol marks the place where torturous executions were once carried out.

A beautiful Greco-Roman structure houses a well once believed to have healing powers.

An American ghost town hides along a side street in Scotland's capital.