One of the deepest indoor swimming pools in the world.

Three floors of musical instruments coming from all corners of the world and hundreds of years of musical history.

An elegant chandelier hangs over this ancient sewer chamber, now open for concerts and public tours.

This historic funicular system combines the old with the new while offering delightful views over the surrounding valley.

This unique exhibit "Dialogue in the Dark" reverses roles as the visionless become guides and the sighted become ‘blind.’

This museum in the famously blue neighborhood of Sidi Bou Saïd showcases a traditional Tunisian lifestyle.

This tipsy office building in downtown Prague was originally called “Fred and Ginger.”

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

Countless grotesque faces stare out from this eerie Prague art wall.

This stucco building in North Africa was the first American-owned property on foreign soil.

Along the most northwestern point in Africa is an ancient cave surrounded by legends.

A church filled with the bones of hundreds of virgins martyrs—or so they say.

The big toe of this towering monument to a Croatian national hero is worn from years of superstitious rubbing.

This unique structure allowed boats to bypass underwater mine barriers in the channel to enter the harbor.

Now abandoned, the world's first torpedo factory is crumbling into the sea.

The 2,000-year-old Roman columns are hidden within Barcelona's Gothic Quarter.

In Spain, the ruins of a Roman military camp sit along a flooded section of a river.

Electrical curiosity museum housed in an old transformer station.

A series of caves under Castle Hill that once held the prisoner Vlad Tepes, better known as Count Dracula.

This oddly beautiful water cistern is a techno-temple to the wet stuff and a multimedia masterpiece.

This column celebrates Rome's victory over the Goths, and may be the oldest Roman monument in Istanbul.

Step back in time and witness the fall of Constantinople.

This former Masonic lodge has been transformed into part museum, part bar, all awesome.

Once a beautiful palace, this structure is now known as the ''museum of destruction."