America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

A collision of human error and natural geothermal pressure created this rainbow-colored geologic wonder.

Inside this mansion turned museum, the works of prominent Croatian artists are on full display.

The oldest arboretum on the Dalmatian coast doubles as the gardens of Kings Landing in "Game of Thrones."

When a supermarket opened up shop within a medieval building it became protected by UNESCO on a technicality.

Humble beginnings for one of the world's most famous scientists.

The complex has been abandoned since the Croatian War of Independence, barring a stint as a set for 'Game of Thrones.'

Legend has it fairies gathered at the site of this medieval castle.

A musical instrument played by the sea.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

An ethereal glowing blue ocean cave in Croatia.

Five sultans and their families rest in eternal splendor, teeming with overlooked beauty and drama.

A marvel of Byzantine engineering under the streets of Istanbul.

A sixth-century Byzantine cistern hidden below a modern carpet store.

This eatery re-creates dishes from the Ottoman Empire so you can dine like a sultan.

This classic restaurant features a gorgeous mirror-clad room.

Visitors can explore the role of mysticism throughout the ages inside this interactive museum of magic.

The bunker where Hitler took his own life is hidden under this deliberately ordinary parking lot.

This Berlin island is home to a flock of free-roaming peacocks, as well as a historic ivory folly.

The largest free-standing aquarium in the world resides in a hotel lobby in Berlin.

This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

A vault of safe-deposit boxes in an old bank has been repurposed as a time capsule of Hispanic culture.

Madrid's last horchata kiosk is a blue-and-white beacon of refreshment.