The national park was once a plantation estate.

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

A celebrity from the late Cretaceous period.

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

D.C.'s first central library was born out of a chance encounter with the philanthropist whose name it bears.

The "lovely red Vega" of the legendary record-settling pilot.

People escaping slavery may have hidden inside a corpse vault.

A computer bug so primitive it was an actual insect.

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

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.

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

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

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 tiny church near Sleepy Hollow contains Henri Matisse's last work, a rose window, and nine windows by Marc Chagall.

Haunted Victorian house that inspired a legendary "Ghostbusters" court ruling.

The footprint of a frustrated devil in Munich's Cathedral.

Golden cobblestones remember a time when this small alley was used to avoid having to give a Nazi salute.

These bronze pamphlets remember a remarkable group of Germans who fearlessly opposed the Nazis in the very center of their power.

A stairway to heaven, or to nowhere at all.

Among the ostentatious rococo ornamentation of this church, an image of death cuts the life-thread.

Daily jousts and dancing barrel makers in Munich's mechanical clock.

The patron saint of spinsters grasps a container of dried blood.

The iconic boulevard is the perfect place to catch sight of a bicycling skeleton, a levitating Satan, or a chef with his head stuck in a pizza.