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

A walk-in working camera obscura produces 360-degree live images of the San Francisco coast.

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

Relics of the 1894 Midwinter Exposition continue to delight visitors today.

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

A tiny theater hidden in an alley plays a constant stream of short silent films for anyone willing to peer through the peephole.

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

A collection of 20th-century automata, penny arcade games, and musical contraptions.

A 140-year-old castle with underground caves hidden in San Francisco.

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

A psychedelic labyrinth on the San Francisco bay.

This Virginia railway overpass is said to be haunted by a serial killer in a rabbit costume.

The ruins of this Thomas-Jefferson-designed mansion have been left to crumble since the Christmas Day they burnt down.

Herbert Hoover's "Brown House" rural presidential retreat was a PR disaster amid the start of the Great Depression.

Once home to seven different roller coasters, Glen Echo has undergone many transformations since its founding in 1891.

A wrecked ship dating back to the American Revolution was only recently discovered off the Delaware coast.

These old doors are covered in the signatures of Rehoboth Beach artists dating back to the 1930s.

Bar full of oddities, specimens, artifacts and homages to the great dime museums of the past.

Atop this media building, two hives containing more than 30,000 bees keep the surrounding area vibrant.

The district's only illusionarium supports free writing programs for local students with every purchase.

This forgotten boat elevator was an engineering marvel in its heyday.

Before Nixon, "watergate" meant canals.

This stately mansion, built in 1787 by America's first Secretary of the Navy, is rumored to be one of the most haunted buildings in Washington, DC.

Four bald cypress trees in Lafayette Square, across from the White House, mark the southern edge of a 100,000 year old cypress swamp.