Old submarine parts have been converted into faux whale fins.

Christ's blood preserved in a Belgian town.

The castle where the Marquis de Sade lived out his darkest fantasies.

This bridge was constructed from the rubble of the infamous Bastille.

The first green space constructed on an elevated viaduct.

A glamorous hotel that once accommodated French resistance fighters and concentration camp survivors.

Paris' fabled purveyor of exotic taxidermy and natural history curios.

Former hunting lodge of a duke who was an avid collector of impressionist works.

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

A Natural History and Science Emporium.

This castle-like building in Manhattan helped destigmatize cancer in the 19th century.

An outsider art duo's yard has been turned into a whimsical public gallery.

A rotting tree in the middle of Seattle doubles as an elaborately-controlled art piece.

The tech giant built three enormous glass orbs in Seattle so employees could work inside a rainforest greenhouse.

This former coal gasification plant found a curious second life as a popular public park.

A museum dedicated to the history and exploration of both popular music and science fiction.

A huge musical sculpture and other art installations on the National Oceanic and Atmospheric Administration grounds.

A stunning landscape of bunkers that once stored chemical weapons.

A memorial to the nearly 10,000 American soldiers laid to rest on the beaches of Normandy during WWII.

This enormous "cloth of the conquest" depicts the Norman invasion of England in mind-blowing detail.

Remains of the artificial harbours invented for the Allied invasion of Normandy can still be seen at sea.

France's most famous cemetery, with some of its most curious tombs.

The ruins of a Duke's bucolic dream, where camels once roamed alongside "Dutch" windmills and faux-Italian vineyards.

The curious underground history of keeping Paris clean.