This naturally-sourced hot spring is now home to a clothing-optional resort.

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

This advertisement for talcum powder was painted on the rock face and has since defied removal.

This rare triple-jurisdiction drawbridge passes through Virginia, Maryland, and Washington, D.C.

A swimming hole in the historic industrial quarry that supplied the marble for the Baltimore Washington Monument.

This massive swimming pool is the high tech home to the human-powered submarine races.

This ruined quarry once produced the distinctive red sandstone used for construction projects in Washington, D.C.

One of the oldest anatomical theaters in the U.S. still in use was once the site of an infamous cadaver riot.

Two dozen pinball games hidden away inside a most unlikely location.

Live data is transmitted from the Atlantic coast to instantly recreate the ocean waves in this fountain at the NOAA headquarters.

This scenic Maryland park was the site of one of the worst prison camps of the Civil War.

This bug-eyed water wheel uses the power of the Sun to clean up Baltimore Harbor.

A faded sign from the 1920s remembers Baltimore's resistance toward banning alcohol.

This simple convenience store sits on the location where the Ouija board was named—and has a plaque to prove it.

A hidden alley in urban Baltimore is a haven for graffiti artists.

A priceless collection of the Nation's cryptologic history.

Bizarre Cavern.

This marker identifies the location where three states converge.

Birds with backpacks expedite film development for a rafting company on a remote Colorado river.

It would be easy to walk past this unusual piece of art and have no idea it pays tribute to the odd life of a real chicken.

The world's largest sticker ball weighs in at a mighty 231 pounds.

A lively annual event in which thousands of people race to push coffins heavy with bodies up a hill.

A stark reminder of the huge nuclear weapons plant that once stood on the site and its effect on the surrounding area.

When zealous marijuana enthusiasts kept stealing the "Mile 420" highway marker, the State of Colorado got creative.