The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

The Conduit Road Schoolhouse is one of the last one-room schoolhouses remaining in Washington, D.C.

The span is crooked and made from two older recycled bridges.

Every drop of D.C. tap water flows through this old waterworks.

This advertisement for talcum powder was painted on the rock face and has since defied removal.

A star fort along the C&O Canal in western Maryland that protected America in three wars.

Despite violent work crews and massive delays this abandoned canal tunnel was built to last into the modern day.

This one-room cabin where the young colonel slept during the French and Indian War.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

With 3,000 bikes on display, the world's largest bicycle museum includes some famous rarities.

A collection of memorabilia from the Beat era in the back of a San Francisco bookstore.

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

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

This colorful boulder serves as a canvas for political statements and artistic expression.

These subterranean storage areas hold emergency water reserves.

This painted marvel is San Francisco's 400-foot ode to urban biking.

This Alamo Square mansion is rumored to have hosted satanic rituals and other occult practices.

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

San Francisco’s century-old Christmas Tree.

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

An elaborate gift from Claus Spreckels is now a piece of San Francisco history.

A hidden subterranean installation offers a view of the sky.

Part mural and part sculpture, this work of art sits in the middle of the Promenade, as if swimming in a river of asphalt towards the ocean.

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