This palatial botanical garden is home to one of the largest pipe organs ever installed in a private residence, and a piece of Wood's cycad.

These tourist trap caverns are said to be the former home of a legendary Pennsylvania Hermit.

Tour the dark and beloved poet's former cobwebbed basement, which may have inspired "The Black Cat."

A toxic ghost town sitting atop a massive coal fire.

A layered tribute to the work of mosaicist Isaiah Zagar.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

World's first "penitentiary," meant to be humane, drove men insane.

A 9-story, poured concrete structure which was used as a glue factory with an indelible smell.

This anonymous businessman sculpted in bronze became an enduring memorial after 9/11, and had been mistaken by rescue workers for a survivor in the rubble.

Before Metro, Washington had a robust streetcar network—and you see the remains of this infrastructure if you know where to look.

Washington's top-secret Cold War-era doomsday communications tower is located in a small neighborhood park.

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

Housing the National Women's Party since 1929, this historic house is now a monument to the fight for gender equality.

A super-sized promotional trick that is now a D.C. landmark.

A wondrous old library overlooking the nation's capital.

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