Concrete strongholds stand guard over the Golden Gate.

A 140-year-old castle with underground caves hidden in San Francisco.

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

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

This concrete tangle of square pipes has stood as a proud thorn in the city's side since the '70s.

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

Olfactory delights in San Francisco's Botanical Gardens.

Golden Gate Park's historic collection of plants.

Since 1973, this block has been home to the most concentrated collection of murals in San Francisco.

The giant pair of sexy legs sticking out the window of this costume store have become its main draw.

Join the circus for a few lessons to learn clowning, acrobatics, and Chinese contortion.

The oldest burial ground in the city, final resting place of city founders, Ohlone natives and murderers alike.

An essential stop before plundering, BYO Cutlass.

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

Elevated freight railway turned wildly successful urban park.

A layered tribute to the work of mosaicist Isaiah Zagar.

Macabre astrological automaton clock dating to the late 1400s.

High on a hill overlooking Los Angeles lives a world famous, high power conical Tesla Coil.

World's first "penitentiary," meant to be humane, drove men insane.

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

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

Pillars made of 700 pieces of luggage climb to the ceiling of Sacramento Airport's baggage claim.

An eccentric home stands out in an otherwise average neighborhood with mosaics, mini topiaries, and kinetic sculpture.

A tiny survivor of the Donner Party disaster.