Forgotten and then destroyed by fire, this was once one of the largest saltwater swimming pools in the world.

A pair of mutilated bronze octopuses slump at the base of the monument honoring California's admission to the U.S.

One of few lasting examples of the brief octagon craze that developed into folly.

A brooding mansion of clinker brick stands out among the Victorian houses of Pacific Heights.

Barely visible foundations remain where Stow Lake’s “observatory” once welcomed visitors.

Gold Rush ship-turned-hotel buried underneath San Francisco's financial district.

A famous alternative culture epicenter and where Joplin serenaded young hippies.

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

Art from the latest counter-culture; kids who dye their hair blue and believe the future will be a post-apocalyptic water world.

A walk down memory lane in the heart of one of San Francisco's most notorious neighborhoods.

Adolph Sutro's little-known, geographically inaccurate, deprecated monument.

A speck of nature and art in one of San Francisco’s most notorious neighborhoods.

Longtime headquarters of controversial boys' club for the world's wealthiest and most powerful.

The miraculous hydrant that saved the Mission District in 1906.

San Francisco's oldest operating hotel, with a Victorian atmosphere and a "haunted" fourth floor.

Half of a house.

A hidden subterranean installation offers a view of the sky.

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

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

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

One of the most elaborate displays of Jellyfish is on display at the aquarium.

At this Minnesota state park you can easily wade across the source of the mighty Mississippi.

These crudely shaped folk giants may be the the second most photographed statues in the U.S.

The famed architect designed this Minnesota gas station of the future with a lookout tower.