An early 20th-century bullring converted into a modern shopping center.

Partially collapsed lava tube and cave system complete with concert hall, underground pond, and unique albino crabs.

The iconic boulevard is the perfect place to catch sight of a bicycling skeleton, a levitating Satan, or a chef with his head stuck in a pizza.

Over two centuries old and counting, Madrid's massive botanical garden contains one of Europe's only desert environments.

The ancient mosaics here are considered among the finest in the world, and serve as a stunning record of Greco-Roman daily life.

Dozens of elegant ceramic tiles decorate these ancient walls, each displaying the Lord's Prayer in a different language.

Squeezing inside this deep, narrow canyon reveals a festival of desert colors.

A "miracle" that seems to produce more holy fistfights than holy revelations.

Taking the subway here means doing so over a bridge located in the middle of an estuary.

One of the newest mosques in a city filled with thousands.

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

The world's first combination ski slope and power plant.

Beneath Denmark's Højbro bridge, a bronze merman and his seven sons forever mourn for the mother and wife who left them for land.

Climb to the top of its spiral spire for spectacular views of Copenhagen.

The old observatory in Copenhagen has a spiral corridor used as a racetrack.

Vortex-shaped aquarium hosts Europe's largest school of piranhas and other ocean creatures.

Vast stretch of tide-pools with a unique Moroccan charm.

The largest madrasa in Morocco once housed more than 900 students within its exquisite walls.

At this rare mosque in Tbilisi, Sunni and Shia Muslims pray side by side.

This architecturally eclectic fortress witnessed centuries of bloody turmoil, including the massacre of its ruling clan.

The secret room where early Bolsheviks cranked out propaganda fliers on a smuggled printing press.

You'll find just about anything in this funky Tbilisi flea market.

This lonely minaret with an unusual decorative symbol is all that remains of a historic Ottoman mosque.

These abundant, over-the-top monuments are so widely scattered that they define the entire compact capital cityscape, often leading to jokes about whether there are more statues than residents.