In Zanzibar, a historic 19th-century palace is a reminder of the world's shortest war.

Elaborate tile work in this railway station tells the story of Portugal.

The smaller of the three towers of San Marino is a former prison inaccessible from the ground level.

High in the clouds of San Marino sits an ancient tower with some curious prisoner graffiti.

This mountain trail inspired Nietzsche to complete his magnum opus.

This sweet-toothed bear searching for snacks has been a symbol of Madrid for decades.

This macabre masterpiece of a mural is one of Francisco Goya's "Black Paintings."

In one of the smallest countries in the world stands an original Salvador Dalí sculpture.

The celebrated eyesore created by starry-eyed sweethearts.

This massive blockhead sculpture hides an entire library.

Historic medieval fortified city in southwest France.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

One of the world's tallest statues is also one of its most hated.

The gorgeous entrances into the city's underbelly look more like grand halls than subway stops.

This building holds the embalmed remains of the leader of the Bolshevik Revolution.

Physicist’s epitaph provides final confirmation to a career of turmoil.

An ornate private entrance to the Vienna subway built specifically for the emperor.

This series of Baroque passageways in Vienna's cultural center mix old architecture with modern art.

Giant WWII fortresses that fired 8,000 rounds a minute, now home to thousands of pigeons.

Vienna's diversity-themed traffic lights were inspired by the Eurovision Song Contest.

Op-art architecture designed for happiness.

This former insane asylum now holds a pathological anatomy museum.

The final resting place for the remains of 143 Habsburg royalty.