A cave's rare beauty held a cavernous secret hidden underground.

Legends surround this jagged rock formation in the New Mexico desert.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

Austria's 5-star prison.

This series of Baroque passageways in Vienna's cultural center mix old architecture with modern art.

A silly medieval mural preserved on the side of a Viennese house.

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

An Austrian house of bones filled with hundreds of intricately painted skulls.

The beautiful baroque library of the Hapsburg empire.

Now harmless, this looming post struck fear into the heart of medieval troublemakers.

Vienna's giant wonder wheel had a starring role in one of the greatest noir movies of all time.

Op-art architecture designed for happiness.

Once the tallest building in the world, this abandoned church is now a monument to the destruction of WWII.

This dockworkers' lunch joint has been left leaning by a century of storm floods.

Hamburgers are intensely proud of their tunnel beneath the river.

Cozy basement bar sports an inventory of over 2,000 beers.

Elaborate tile work in this railway station tells the story of Portugal.

One of the most beautiful bookstores in the world hides a neo-Gothic interior behind an art nouveau facade.

This restored Portuguese cafe may well be the most beautiful place in the world to grab a Big Mac.

A musical instrument played by the sea.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

One of downtown Berlin's last reminders of its Communist past.

A massive underwater sinkhole made famous by Jacques Cousteau.

A former waterfront market is now in the center of town due to some interesting Boston engineering.