A haven for book enthusiasts across the street from Retiro Park.

The lengthy skeleton of one of the tallest Spaniards of all time is on display in Madrid.

This small exhibition displays equipment and artifacts once belonging to the feared Stasi secret police.

Oberweissbacher Bergbahn - a broad-gauged cable car capable transfering railcars.

A Belgian self-built tower inspired by the Bible and ancient civilizations.

An art world insider finds himself battling for his artistic home.

A fake medieval village in the middle of Turin.

Amöneburg is a town perched on top of a basalt mountain in the middle of an ancient meteor crater.

Ancient man-made caves underneath small town Belgium.

Hiding the longest subterranean river known in the world.

Vast network of air raid tunnels beneath Lombardy's capital.

Natural cathedral designed by Italian artist Giuliano Mauri.

Old batteries and frog skeletons reside in this lakeside monument to Alessandro Volta.

An ancient artistic garden parlor full of hidden water wonders.

The birthplace of an eccentric alchemist and possible inspiration for the fictional reanimator of monsters.

Over 3km of caverns and caves at the Switzerland-France border contain the largest underground river in Central Europe.

Go surfing on this urban wave, "hacked" by local surfers.