The miraculous hydrant that saved the Mission District in 1906.

A huge musical instrument played by the ocean.

17th century streets hidden under Edinburgh were once a breeding ground for the black death.

The most loyal of little dogs, or a Victorian era publicity stunt?

Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

Home to items never before seen by the public.

At 207 feet, one of the world's longest continuous escalators.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

'Cause the fence start shaking, the earth was quaking.

One woman's Viking Castle on Lake Tahoe.

A nondescript building that's been functioning as a speakeasy for nearly a century and a half.

A shop full of natural curiosities, carnivorous plants, and costumed taxidermied mice.

A library built during San Francisco's pioneer times is a student's retreat, bibliophile's sanctuary, and chess player's delight.

Northern Ireland's Brobdingnagian stepping stones.

The bears of Bern have been a city highlight for over 500 years.

Synagogue built from the stones of Solomon's temple contains the golem of Prague.

One of Ireland's most infamous prisons for rebels including men, women and children.

The ancient tomb acts as a calendar that keeps perfect time.

Children's hospital in London that operates on royalties received from Peter Pan, which J.M. Barrie signed over in 1929.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

Where commuters walk through remnants of an ancient Greek necropolis.

The hallucinogenic center of the ancient world.