The Cold War-era "underground Pentagon" is a sprawling subterranean hideaway for the Defense Department.

A labor of love built by local hang-gliding enthusiasts, this ideal launch spot was outlawed by the authorities and has since been largely abandoned.

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

The rock on which Moll Dyer was found frozen to death is said to still bear her handprint.

The 3.8 billion-year-old rock proves that tectonic plates may have been shifting longer than we thought.

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

This four-story steel sphere in Maryland was used to test biological weapons.

Historic barracks utilized during both the Revolutionary War and the Civil War.

A unique marker erected during the 18th century.

The land is home to swimming ponies and a legendary 18th-century treasure.

An isolated island home to one of the oldest English-speaking communities in the region and Maryland's state dessert.

The final resting place of an iconic drag performer is decorated with pearls and hot-pink lipstick.

A small museum along the Susquehanna River is home to a rich collection of Native American artifacts.

The meeting of the northwestern corner of Delaware, the northeastern corner of Maryland, and the southern edge of Pennsylvania.