A glimpse into the sacrifices of military members during World War II.

Long buried under the 20th-century landscape, this lift lock of the Alexandria Canal is the lone remnant of an ambitious early American transportation project.

Politicians, bureaucrats, and military officers gathered in this field near the Capitol to settle their disputes with blood.

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

The United States Capitol's former columns still stand.

One of the dwarven trees dates back to 1625 and survived the Hiroshima bombing.

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

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

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

This statue of one of baseball’s greatest pitchers looks like something out of a sci-fi horror movie.

This lonely waterfront memorial to the men of the Titanic was erected by the "Women of America."

One of the first Second Empire-style buildings constructed in North America.

This site is believed to be connected to the oldest house in Arlington County.

The country's oldest continually-operated mini golf course lies hidden in plain sight, eclipsed by one of D.C.'s most popular tourist attractions.

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

The Pentagon sits on a former island that was in Virginia at low tide and D.C. at high tide.

Rumor has it the uncarved lump behind the three famous suffragists is reserved for the first woman president.

A celebrity from the late Cretaceous period.

The site of the climactic scene from the classic horror film is now a historic landmark.

An unassuming, powerful monument north of the U.S. Capitol bears witness to the resilience of Japanese Americans during a time of grave injustice.

The national park was once a plantation estate.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

A historic estate packed with George Washington's heirlooms, and its own nuclear bunker.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.