A Spiritualist house of worship where believers communicate with the dead in the spirit world.

This leafy estate is worth $18 million and is so grand it has two mailing addresses.

A haunting tribute to pioneering photographer Clover Adams.

A nostalgic bibliographic gem.

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

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

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

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

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

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

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

Home to items never before seen by the public.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

The United States Capitol's former columns still stand.