Catacombs turned marketplace.

The curios of pharmacist and collector Henry Wellcome.

A hands-off space for graffiti artists to hone and display their skills.

The only university zoological museum in London houses extinct animals, bizarre natural history specimens, and a Micrarium of microscopic creatures.

What looks like a normal building is really a hollow facade hiding a subway vent.

Natural history museum celebrating biodiversity with a parade of taxidermy animals.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

A haunting collection of the vanished and disappearing natural world.

The unusual sculptures are believed to be powerful political symbols.

A towering spire in the fortress of Kalemegdan honors the victorious armies of Serbia during their struggles against the Ottoman Empire.

A misnamed well, with a deep dark past.

Destroyed Serbian army headquarters sits half crumbled in a largely revitalized Belgrade.

A pair of connected skyscrapers form this symbolic gateway.

A Serbian church lit by chandeliers made of weapons.

Nikola Tesla's ashes are held in a golden sphere, surrounded by his works.

This crumbling medieval basilica once attracted pilgrims by the thousands to collect a miraculous dust that formed above the saint's tomb.

This historic hotel preserves many treasures from its heyday hosting passengers on the Orient Express.

Legend says if you stick your thumb in the hole and it gets wet your wish will be granted.

The legendary luxury train passage is commemorated with a charming museum inside its former eastern terminus.

The ancient latrines of the Greeks, in all their public glory.

A charming beach town in Turkey captures all the colors of the rainbow.

Ancient serpentine sacrifice holder that has stood the test of time.

A small etching on the white marble parapet was written in runic script by a Viking mercenary.

Mediterranean castle on a tiny Turkish island.