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

The seawater playground of gilded-era San Francisco burned to the ground in 1966.

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

A favorite haunt of dinosaur loving children and hallucinogen loving hippies alike.

A pair of slides and a tree-lined stair corridor have been an urban oasis for nearly 40 years.

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

Get lost in this haunting fairytale art walk through a man-made eucalyptus grove.

A winding path built in secret on the edge of the continent.

This shop specializes in oddities and Victorian-inspired wonders.

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

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

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

A huge musical instrument played by the ocean.

A focal point of in Denver’s skyline for over a century, inspired by a Venetian basilica.

The huge collection of paintings of the American West is one of Denver's best-kept secrets.

The spot in the Mile-High City that's exactly 5,280 feet above sea level (at least for now).

A downtown park built on top of unclaimed graves.

A small horde of mythical creatures lurk almost imperceptibly within the museum's wildlife dioramas.

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

The Denver airport is guarded by a 32-foot-tall sculpture of a demonic horse.

Religious dwelling in a Spanish volcano.