Before founding the American Red Cross, Clara Barton had a tremendous humanitarian impact by locating thousands of missing soldiers.

A hoard of sky catalogs, astrophysical journals, even the works of Galileo and Copernicus.

It was once the base for a series of domestic terror attacks.

Home to a vast and influential collection of Shakespeareana.

This unique museum cafeteria showcases the history and regional diversity of African American cuisine.

This quirky curiosity shop takes its cues from the world's bazaars.

A pink and gray pair of pachyderms advertise a fireworks shop.

The final resting place of the "father of special effects."

A nature and cultural preserve named for its multitude of petroglyphs carved by the Northern Sinagua people.

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

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.

The only Civil War battle in Washington D.C. took place near this highest natural point in the city.

There’s a special club house at the top for the bell ringers.

The institution is sitting on a goldmine of 21,000 paints, varnishes, pigments, and primers preserved for posterity.

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

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.

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

The 320-year-old tree that greeted General Lafayette and rerouted an interstate highway.

The controversial urban planner who designed Washington, D.C., was buried in Maryland, and can presently be found in Virginia.

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

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

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.