Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

The most visited, and possibly most controversial, museum in Germany.

A walk-in working camera obscura produces 360-degree live images of the San Francisco coast.

Macabre astrological automaton clock dating to the late 1400s.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

This geothermal hot spring hides beneath a slowly growing mineral dome.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

Famously misunderstood wonder of the ancient world

Olfactory delights in San Francisco's Botanical Gardens.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

Relics of the 1894 Midwinter Exposition continue to delight visitors today.

Carnivorous plants, medieval aphrodisiacs, and the largest original wood structure glass conservatory in the western hemisphere.

The first declared National Monument in the United States.

The deepest lake in the United States, and once the site of epic destruction that lives on in legends.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

The fairy tale castle of the "fairy-tale king."

Medicinal spa created with the discharge from a geothermal energy plant.

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

Elevated freight railway turned wildly successful urban park.

France's most famous cemetery, with some of its most curious tombs.

Dodge prohibitionists and slide through the telephone booth in Crif Dogs.

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

Dramatic river bend surrounds a natural red-rocked pedestal.

Most-visited and most-photographed slot canyon in the American Southwest.