A shady solar power system that couldn't hold up to the harsh desert conditions.

Visitors to this library are in for a real-world education in modernist architecture.

Hundreds of drawings left by the land's previous inhabitants remain mysterious.

The notorious headquarters of a corrupt political machine.

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

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

Under a glass sidewalk lie the remains of some of Manhattan's oldest buildings.

One of the largest collections of Catalan literature and cultural materials outside of Spain, created by a community of 1960s expats.

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

There's a crumbling old mansion inside the Smithsonian National Zoo.

The Byzantine, pre-Columbian, and medieval art at this stately mansion are some of the most under-appreciated collections in D.C.

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

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

A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

This grisly headstone doesn’t seem to be resting in peace.

Walk through the history of American pop culture.

Home to items never before seen by the public.

Dogs, cats, horses, monkeys, frogs, and fish are laid to rest at the second-oldest pet cemetery in the U.S.

This dig site outside D.C. is known for its exceptionally high density of baby dinosaur fossils and dinosaur eggs.

Walk a trail through a historic Quaker town that outlawed slavery in 1777 and was a major waypoint on the Underground Railroad.

The first piece of public art dedicated to LGBT rights.

Possible relics of the ancient Roman city are hidden in this restaurant's façade.

This curved Manhattan building was built to house the opulence of John D. Rockefeller's oil empire.

Built hundreds of years ago this downtown iron barrier once protected a much despised king.