Erotic art covers the walls of the largest ancient pleasure palace.

This picturesque Umbrian city has a subterranean side that has long remained hidden.

The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.

The Pope’s secret escape route.

This shining multicolored metro station deep under Naples is said to be the most beautiful in Europe.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

The glowing blue Nymphaeum of Emperor Tiberius.

Hidden in the Santa Ynez Mountains off Highway 154, this tiny restaurant once served as a stagecoach stop.

Depicting scenes of everyday life - and specific individuals - in Great Depression era San Francisco.

One of the oldest producers of hand-folded fortune cookies still uses its original secret recipe.

Golden Gate Park's historic collection of plants.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

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

Julia Morgan's Moorish-Gothic labyrinth of fountains, trees, natural light and Oakland's notable dead.

Belgium’s famous peeing statue has worn many hats (and coats, and pants), which are on display at this small museum.

A lovely biographical museum in the artist's home of 24 years.

A little sculpture with a large wardrobe.

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

One of the greatest heroes of the Titanic tragedy came from humble beginnings to this beautiful home.

Overlooking the Colorado Convention Center is this giant sculpture made from thousands of triangles.

Non-profit time travel mart sells goods you would need for a trip through the fourth dimension.

Montmartre's sole surviving windmill became an iconic landmark for 19th-century painters, artists, and bohemians.

This small, ingenious cannon once helped regulate Parisian life.

One of Jeff Koons’s largest sculptures and his first commemorative work.