The historic “pink house on the hill” is an architectural gem that now serves as a center for water conservation.

A museum and tribute to a brave profession.

A geological mystery on Camelback Mountain.

A diminutive plaque recalls the treetop sniper who almost killed Abe Lincoln.

Cold War intelligence agents monitored communist embassies from an attic in a former pigeon coop.

You could be standing at the site of one of D.C.'s most fatal tragedies and not even know it.

There's a crumbling old mansion inside the Smithsonian National Zoo.

An obscure federal monument honors the French diplomat who served as Ambassador to the U.S. during WWI.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

The largest natural travertine bridge in the world is nestled in a small canyon in central Arizona.

Colorful Native American paintings are hidden within this small cavern.

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

Four hundred granite steps were built into this massive rock by the National Park Service.

Quite simply the largest tree in the world (by volume).

A 19th-century cabin built into a hollowed-out Sequoia tree.

A pre-Industrial Age iron furnace and the site of a nearly-forgotten piece of Black history.

Unannounced visitors are now welcome at the site of the largest Prohibition-era bootlegging operation in the region.

Where decommissioned airplanes and helicopters go to become part of Hollywood.

The "Kill Bill Church" was transformed into a place of worship after a long Hollywood history.

A colorful, century-old cemetery of the Yaqui Indian Tribe hidden amid the suburban sprawl of Tempe, Arizona.

This methodist cemetery is slowly receding into the wilderness along a Maryland highway.

The oldest building in the District of Columbia was preserved because of a mistaken connection to George Washington.

A historic ruin just 20 feet away from a busy highway onramp.