San Francisco's newly reopened hands-on science museum.

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

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

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

This iconic L.A. bookshop is housed in an abandoned bank—both symbolic and chic.

An artsy hidden staircase leads to breathtaking views of San Francisco.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

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

This historic Victorian hotel has a scandalous history of affairs and murder.

The narrowest street in Canada was once a spot for dastardly doings, now a historic piece of Chinatown.

What happens when a sculptor has to find a way around a 100-year-old copyright.

If you can look past the nearby sewer pipes, this urban sinkhole grotto is a mini-paradise.

Every equinox this Maya pyramid puts on a spooky ancient light show.

One of the largest underground systems runs under Canada's largest urban center.

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

A historic observatory precariously perched at the "Top of Europe."

This historic covered bridge contains a series of macabre paintings that communicate one thing: everyone dies.

This memorial commemorating fallen Swiss Guards of the French Revolution has been called the saddest stone in the world.

Two stone columns flank the grand Venice square, but there were supposed to be three.

Go inside to really appreciate this 500-year-old technological masterpiece.

A slightly creepy gallery of plaster cast models in the same museum as Michelangelo's David.

The middle finger of modernity.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

The oldest working mechanical clock in the world.