Barcelona's historic 19th-century sewers, whose foundations were laid in medieval times, are open to the public for exploring.

A temple to modernity, tucked away amid Barcelona's more well known museums.

This cafe offers a curated collection of treats and tipples made by monks and nuns.

Macabre museum devoted to historical Viennese murders.

Home to 10,000 medical specimens including the remains of Rudolf Virchow's extensive collection of pathological specimens.

An eerie, derelict amusement park in Berlin.

Since ancient times these picturesque springs have been providing bathers with healing waters.

This 17th-century manor house provides a fascinating glimpse into old-world Mallorcan life.

This historical manor is complete with a magnificent garden.

Be(w)ar(e) the moat around this historic Czech castle.

Heralded as one of the prettiest castles in all of Czechia.

A steampunk-styled three-floor factory churning out art, activism, and electronic beats.

The history of occult science is turned into a creepshow at this lurid Prague tourist attraction.

A museum devoted to bringing to light forgotten or neglected histories through exhibitions, education and public programming.

The humble fort that saved Washington.

A New York garbage depot holds a secret collection of weird and wonderful refuse.

Check out the underground party scene at the "Burning Man of Brooklyn."

An arcade packed with a rotating collection of unique independent video games.

According to a local legend, this old castle could only be built after a woman was immured in the walls.

What happens when you cross a mayor and a painter?

In this town's main square resides a statue of none other than the 43rd President of the United States.

Bronzes and busts that once stood in the city's main squares are now relegated to a small hidden courtyard.

Once the fallout shelter of a dictator, this sprawling bunker is now a combined history museum and contemporary art gallery.

A medieval bridge stretches over a sulfur-rich river that leads to year-round natural hot springs.