There’s a hidden military meme engraved on the World War II Memorial.

The national park was once a plantation estate.

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

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

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

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

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

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

A tiny piece of the Moon is embedded in this stained glass masterpiece.

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

The United States Capitol's former columns still stand.

Site of the first pathological and bacteriological research facility in the United States.

One of only two commuter aerial tramways in the United States.

Avoid gangster interaction while window-shopping.

Once the tallest building in the world and the site of "the highest dinner ever held in New York" this building now holds the most expensive penthouse in the city.

The last living thing to come out of the rubble after 9/11 is now a symbol of hope and resilience.

Pulled from the rubble of one of the worst modern tragedies, a steel crossbeam became a symbol of hope for New Yorkers.

This sculpture by artist Fritz Keonig survived the 9/11 attacks and now stands as a monument to the victims.

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

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

Twice a day one of these tragic bronze mariners drowns with the tide to remember all those the sea has taken.

Ride the subways of yesteryear.

A crumbling hospital from the 1850s on Roosevelt Island.

Colorful boxes placed over the dead are left to rot and crumble.