The world's second-longest burning light bulb.

Washington's iconic carousel has a nice piece of Civil Rights history.

An overlooked oasis of quiet on the grounds of Washington's monumental basilica.

More than 500 unique and specially designed cases collected by D.C.'s "Harmonica Case Man."

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

A celebrity from the late Cretaceous period.

There’s a hidden military meme engraved on the World War II Memorial.

The national park was once a plantation estate.

‘Bush the old fire dog died of poison July 5th, 1869. RIP.’

This robust fence in front of a historic Georgetown home is likely made from hundreds of recycled Revolutionary War firearms.

A small token of gratitude from freezing cold journalists who were given a warm haven while covering JFK's inauguration.

A rotating cast of guys and dolls in front of a Washington, D.C. building.

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

These recently uncovered walls are all that's left of Washington, D.C's first defense contractor.

Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

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

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.

Behind an abandoned storefront is an example of pioneering 1930s gas station architecture.

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

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

One of the largest artillery pieces in the world sits in a Washington D.C. parking lot.

A clone of a cloned tree that was so important it allegedly had its own guards.

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

This sandwich shop has a century-old elevator behind a sheet of plexiglass.