In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

The largest bell in the world has been swinging high above a Cologne cathedral for almost a century.

Thousands of tourists and residents in Cologne affix "love padlocks" on the Hohenzollernbrücke Bridge to symbolize their affections.

A giant roundabout made up of six smaller roundabouts can befuddle the uninitiated.

This man-made waterfall was designed to help improve access for spawning salmon.

Old-fashioned knowledge and modern engineering create the world's only rotating boatlift.

The heads of two giant mythological water horses honor Scotland's horselord past.

Hear the quietest sound from across the dome.

The bridge is a secret gallery of discarded gum that has been transformed into miniature masterpieces.

This one has sailed five times as far as Sir Francis Drake's famous ship.

Ship-sized kinetic sculptural fantasy.

Catacombs turned marketplace.

The rose garden in Regent's Park where Pongo and Perdita met for the first time in Disney's "101 Dalmatians."

The anatomical-pathological collection of a man who changed surgery.

Eighty million natural history specimens call this gargantuan museum home.

Charles Babbage's proto-computer, painstakingly brought to life.

A fascinating insight into daily life in the Eastern Bloc.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

A minotaur, a labyrinth, and a dubious restoration pull in visitors from around the world.

A 150-year-old steam locomotive crosses the southern half of the island daily.

This natural wonder is disappearing at an alarming rate.