The winter home of millions of migrating monarch butterflies.

Gilded heaven for philatelists and architecture freaks, still in full working order despite sitting atop tremulous ground.

The only castle in North America to ever house European sovereigns.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

High atop a Mexican rainforest mountain, this ancient pyramid once drew pilgrims countries away.

Every equinox this Maya pyramid puts on a spooky ancient light show.

This abandoned hospital is one of the most haunted places in Costa Rica.

These mysterious ancient stone spheres were created by a civilization lost to time and are now mostly lawn ornaments.

A pair of connected skyscrapers form this symbolic gateway.

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

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

Home to more than 13,000 pieces of war memorabilia and military equipment.

Once a black market electronics marketplace, now an otaku shopper's paradise.

Not quite the menace it once was, this monster still has some chops.

Cabaret where the show girls are all androids, and the patrons couldn't be more pleased.

Elevated freight railway turned wildly successful urban park.

Disney's abandoned animal island is now an overgrown ruin that was almost the coolest attraction ever.

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

On a winding Vienna side street, one museum has turned their windows into a monument to history’s peace-minded heroes.

The Habsburgs' royal collections of art and wonders.

Dine amidst exotic plants at this former royal greenhouse.

Baroque celebration of the end of the Great Plague of Vienna.

Built to give thanks for the passing of a plague epidemic, this cathedral is a one-of-a-kind architectural hybrid.

The beautiful baroque library of the Hapsburg empire.