The oldest surviving one-room schoolhouse in Montgomery County, Maryland.

The semi-reclaimed ruins of this canal were once part of an ambitious plan to reroute the mighty potomac.

The ruins of this long-abandoned unsuccessful gold mine can still be found.

This massive swimming pool is the high tech home to the human-powered submarine races.

The bridge's highly-contested plaque (once again) honors Confederate President Jefferson Davis.

These abandoned waterworks are crumbling into the Potomac River.

This lovely picnic spot featuring thunderous jet landings is an aircraft spotter’s dream.

The 72-foot giant escaped confinement in a large patch of mulch only to be reburied in the sandy shores of the Potomac River.

America's first federal monument.

This stately building in Alexandria, Virginia was built by Freemasons to honor one of their most famous members.

This cannon dating to 1755 has stood guard at this suburban intersection since 1915.

Three and a half miles of cliffs, rocky beaches, Gilded Age mansions and 40 Steps to nowhere in particular.

Surprisingly aquamarine waters fill deep lakes formed at the end of the last ice age.

This Art Deco fortress in upstate New York gives Manhattan's vaunted examples of the style a run for their money.

A toxic ghost town sitting atop a massive coal fire.

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

A bunker "with enough U.S. currency to replenish the cash supply east of the Mississippi" in the event of nuclear war now protects nitrate film.

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

Look closely and you’ll notice that the color changes a third of the way up the tower.

The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.

Washington's top-secret Cold War-era doomsday communications tower is located in a small neighborhood park.

A historic arena where the Beatles played their first concert in the U.S.

A building shaped like the Army Corps of Engineers logo, because why not?