Once part of a dam servicing an early 19th century grist mill, the tucked-way falls are a tricky-to-find urban oasis.

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 fort down the Potomac from Washington, D.C. was once the only defensive fort protecting the capital.

Built by the patriotic residents of Boonsboro in a single day.

A Civil War Museum with some notable medical antiques.

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 abandoned sea fort has become an accidental bird sanctuary.

An eerie, abandoned military base engulfed by nature and graffiti is now home to a local park.

A cave on the Maryland border where civilians took refuge during the bloodiest battle of the Civil War.

Despite violent work crews and massive delays this abandoned canal tunnel was built to last into the modern day.

Walk a trail through a historic Quaker town that outlawed slavery in 1777 and was a major waypoint on the Underground Railroad.

This English-inspired Maryland garden is home to acres of opulent plant life including bushes shaped into an entire fox hunt.

This free, take-a-book shop seems like a trick but isn't.

The trials and tribulations of marking Poe's grave.

Accessible only by boat, this centuries-old island fort never saw troops or combat.

This candy-striped tower is the farthest east you can go in the United States.

A monument marks the beginning of the longest north-south road in the United States.

A giant telephone commemorates the last "crank" call ever made in the U.S.

A century after his death, this covered bridge still calls to mind the plein air painter who loved it.

The largest tidal whirlpool in the Western Hemisphere.

A precariously balanced rock perches on the edge of a cliff created tens of thousands of years ago by glacial erosion.

This 19th century granite fortification is one of the most well preserved forts in New England.