Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

A tiny monument to the unsuccessful attempt by Thomas Jefferson to place the prime meridian in Washington.

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

The grand marble structure next to the White House is Andrew Carnegie's temple to Pan-American diplomacy.

Through the decades, Black music stars have performed at this historic hub for music and the arts.

A gorgeous mural outside a beloved D.C. restaurant pays homage to famous Black Americans.

The first memorial dedicated solely to the Black troops who fought for the Union.

The air force base preserves its scars from the Japanese attack on Pearl Harbor.

An authentic replica of an Asian temple and garden hidden amongst the natural beauty of Hawai'i.

This museum of Hawaiian and Polynesian culture is the legacy of the last descendant of the Kamehameha Dynasty.

L. Frank Baum wrote part of the "Wizard of Oz" series in this wooden Victorian beach resort.

A magnificent waterfall nestled in the heart of the El Yunque National Forest.

The abandoned remains of this once-thriving hotel looms over the city, awaiting an uncertain future.

The bat-covered home of one of the world's most popular brands of rum is located on a tropical Art Deco campus.

The world's second largest single-dish radio telescope, once used to contact E.T.

Daredevil repair workers can worm their way out the access hatch, loop ropes over the apex and rappel down the monument.

Built by the patriotic residents of Boonsboro in a single day.

A bas relief commemorates the "Nuns of the Battlefield" who cared for soldiers on both sides of the conflict.

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

The iconic D.C. restaurant where the Cuban Missile Crisis was negotiated, now a Walgreens.

The bank that helped fund the Mexican-American War and the purchase of Alaska met its downfall after helping Augusto Pinochet launder money.

Decades before the scandal, this staircase on the river was a literal "water gate."

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

A much-maligned monument to teetotalism.