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

This curious sculpture represents the perseverance needed to take to the skies.

This Parisian café is dedicated to great tea and the art of knitting.

An off-the-beaten-path boutique stuffed with an eclectic collection of upcycled goods.

Over 120,000 curious objects that have shaped our modern world.

12,000 sq. ft. museum tracing erotic art from antiquity to modern times.

This collection of illusory paraphernalia has been culled from the history of London's premier magician's club.

The library houses an incredible collection of some of the world's most impressive books and manuscripts.

Renaissance hospital featuring a rotating door into which unwanted babies were dropped.

The narrowest street in Paris.

Noirish green neon marks the location of one of the oldest private detective agencies in France.

Down a cobblestone alleyway is a museum dedicated to Romanticism, with a secret garden.

A surrealist timepiece by the artist of melting clocks.

A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.

Notorious artist squat renovated into legal studios.

These Stalin-era industrial 'death traps' hang lifeless above the city

Fast food feels like fine dining at this award-winning modern Georgian building.

The cave holds a spectacular array of stalactites and stalagmites, including one shaped like a giant human heart.

Rock-hewn monastery complex with hundreds of cave structures tucked away into the mountainside.

18m long sarcophagus of a constantly growing dead prophet.

This "tower of death" has acted as an observatory, a religious hub, and an executioner's lair.

This 20th-century mansion plays a key role in one of Puerto Rico's greatest novels.

Years of neglect and nature took a toll on this 19th-century lighthouse.

This former sugarcane transport tunnel is now a portal to a lovely beach.