Scattered throughout London are ancient remnants of the city's former bounding wall.

A museum in the former home of Marxist revolutionary Leon Trotsky.

The only castle in North America to ever house European sovereigns.

Frida Kahlo's childhood home, now a museum of her life and works.

An art supply shop holds the secrets of this quiet neighborhood's raucous Barbary Coast past.

Faceless white figures loom over the city from the rooftop.

An overlooked and unassuming engineering marvel.

The remains of a ruined mansion memorialize the 1906 earthquake.

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

Jurassic Park—A Still Life.

Largest man-made excavation on earth!

Visitors to this library are in for a real-world education in modernist architecture.

These stark white cliffs were spat up by the sea and are slowly being retaken by it.

San Franciscans leave gifts and messages for the magical beings that live behind the tiny, mysterious door installed on a tree in Golden Gate Park.

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

A shining, cold, black organ lies in San Francisco's financial district.

Created in 1972, the famous sculptor's intricately detailed monument to San Francisco is overflowing with city landmarks.

A miniature view of the park, caught in time.

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

Approximately 250,000 people left homeless by the great earthquake and fires found shelter in Golden Gate Park.

Recovered from the brink of extinction, at home in the Financial District.

A psychedelic labyrinth on the San Francisco bay.

Elvis's own personal tropical hideaway.

The hotel where Martin Luther King Jr. was shot is now a museum dedicated to his work.