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

The world's largest model of our planetary system.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

This Denmark theme park is part family attraction, part experimental archaeology project.

The original home of the Lego has a huge amusement park dedicated to the iconic plastic toy.

The world's largest maze is a nature park with nearly 200 decision points.

A serpentine highway twists and turns over the treacherous Norwegian Sea.

This giant boulder is pinched over a 1000-meter abyss by two mountains.

Home to three historic ships from the age of Vikings.

A stunning silver lining to global warming's gloomy cloud.

This Budapest bar allows drinkers to leave their mark on the walls, floor, and even ceiling.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

A marvel of Byzantine engineering under the streets of Istanbul.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

A 2,000-year-old computer demonstrates remarkable engineering and astronomical precision.

The Avenue of Mausolea is a series of grand palatial tombs.

The oldest operating pharmacy in the world features 800-year-old recipes.

Rusting ships sit in a desert where a sea used to be.

A modern tower, symbolizing the legend of a golden egg on top of the tree of life.

An entertainment center in a huge transparent tent.

The most alien-looking place on Earth.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

The glowing blue Nymphaeum of Emperor Tiberius.