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

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

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

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

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.

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

A painfully obvious spy house sits right across the street from the Russian Embassy.

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

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

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

A wondrous old library overlooking the nation's capital.

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

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

Home to items never before seen by the public.

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

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

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.

Love, knishes, and best wishes from this legendary Lower East Side bakery.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

Sniff the Titan Arum's rotting flesh.

Order scoops of pandan, lychee, and black sesame at this family-run institution.

Elevated freight railway turned wildly successful urban park.

This beautiful building in the heart of Manhattan's Financial District was empty for decades.