Concrete strongholds stand guard over the Golden Gate.

An abandoned Jazz Age dream home and con man's hideout in Death Valley.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.

A former poultry store that looks like a giant duck and is one of the "seven wonders" of Long Island.

The most confusing clock in New York.

Elevated freight railway turned wildly successful urban park.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

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

A winding path built in secret on the edge of the continent.

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

This private residence was the template for one of the most beloved television homes of all time.

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

Read between the lines of the subway map to find the hidden abandoned Civil War fort.

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

The rocks in this arid basin leave trails of movement behind them.