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

The design of this historic domed church was influenced by Thomas Jefferson and intended as a statement of religious freedom.

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

Bubbling up from deep underground is the warm crystal clear water that fills the Warm Springs Pools, America's oldest spa.

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

This abandoned sea fort has become an accidental bird sanctuary.

The final resting place of the tragic king and queen of the Jazz Age is tucked away in a small Maryland graveyard.

A 200-year-old bar with a cheeky name claims to have served Edgar Allan Poe his final drink.

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

The remnants of a wooden-hulled fleet built and abandoned in WWI, now home to a thriving ecosystem.

A priceless collection of the Nation's cryptologic history.

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

Bizarre Cavern.

The site where Poe "in great distress, and ... in need of immediate assistance" likely died.

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

It's not hard to see why the historic Peabody Conservatory of Music's library has been described as a "cathedral of books."

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

A grotesque Fiji merman dwells within this traditional Dutch-style building.

Museum houses an impressive display of the origin and artistry from the now-quaint invention's history.

Hundreds of antiquated typewriters and office machinery show the technological evolution of business.

This collection of odd proofs of concept is like taking a walk through the imagination of a Victorian engineer.

This tribute to the founding father of the American dictionary originally contained a spelling error.

It was founded by Ralph Nader to educate the public about an often-maligned area of law.

The Connecticut village named for its subterranean thunder.