Wedged between two buildings at the Great Ormond Street Hospital is this secret music installation.

The remains of a ruined mansion memorialize the 1906 earthquake.

Olfactory delights in San Francisco's Botanical Gardens.

A hidden subterranean installation offers a view of the sky.

Art in the form of a winding, man made crack in stone.

An unassuming grey box sitting on San Francisco's Pier 17 is a "sky diary" of the coastal city's temperamental weather.

Visible below the waves are memorials to the city's Gold Rush dead.

Gold Rush-era tombstones line the park's paths.

These subterranean storage areas hold emergency water reserves.

The only theatre in the world constructed specifically for sound movement.

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

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

Nestled in the heart of San Francisco’s bustling Financial District stands a unique homage to the Mayan and Beaux Arts.

Faceless white figures loom over the city from the rooftop.

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

A Barbary Coast watering hole built into a Gold Rush shipwreck.

This (occupied) house is 10 feet wide and full of spite.

Oakland's beautiful monumental cemetery.

A playground built by the kids that is a child's wonderland, and a helicopter parent's nightmare.

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

A creepy steel gremlin has protected the Bay Bridge since 1989.

A crumbling Beaux Arts monument to the Bay Area's age of rail.

This mysterious series of teeny guerrilla installations sheds a whimsical light on street art in Oakland.