A museum dedicated to exhibiting remarkable outsider art.

The trials and tribulations of marking Poe's grave.

Fascinating museum dedicated to the under-appreciated medical history of urology features some wince-inducing devices.

Remnants of a storybook amusement park hidden behind a strip mall.

The haunting "Hell House Altar" is one of the few remnants of an abandoned college that has been a magnet for local legends.

A local farm's collection of unusual structures from a now defunct storybook amusement park.

This abandoned asylum was once a state of the art facility before devolving into one of the most deadly mental institutions in American history.

Tiny observatory made big contributions to the study of the Earth's motion.

The semi-reclaimed ruins of this canal were once part of an ambitious plan to reroute the mighty potomac.

America's first federal monument.

This grave marks the passing of a historic Jane Doe whose identity remains a mystery to this day.

An original apothecary from 1792.

A former major munitions plant that has been converted into a sprawling art space.

The tallest The Church of Jesus Christ of Latter-day Saints temple in the world soars above the Beltway.

An astounding collection of medical specimens, including bits of President Lincoln.

Giant acorn-shaped 19th century gazebo from which suburban Washingtonians gazed upon the original "silver" spring.

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

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

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.

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

The United States Capitol's former columns still stand.

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

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.