The grounds of former plantations where abolitionist Harriet Tubman spent her youth enslaved are now a museum to her incredible life.

Unannounced visitors are now welcome at the site of the largest Prohibition-era bootlegging operation in the region.

The only retired U.S. nuclear missile silo that is open to the public.

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

Once connected to the outside world by a single train track, this ghost town is looked after by the National Park Service.

Captain John Smith thought these cliffs were amazing in 1608 but sharks thought so 20 million years before him.

This beautiful stone arch bridge wasn't even expected to stand for one day, but people have been crossing it for centuries.

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

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

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

This hidden treasure provides a charming access point along the south side of Baker Park.

Once one of the most polluted caves in America, now an environmental success story and a museum dedicated to caves.

A grassroots community effort in the 1970s led to the creation of this beautiful garden full of delightfully whimsical exhibits.

The Old Courthouse takes visitors on a captivating trip through St. Louis' timeline.

Fresh wooden posts have been added to ancient holes to recreate a primitive henge clock.

Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

Long before guestbooks and hotels, frontier travelers signed their names on this rock face.

The famed architect designed this Minnesota gas station of the future with a lookout tower.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

The longest living non-clonal organisms on Earth.

A gothic palace of endless stalagmites and pseudoscorpions waits within one of the world's most beautiful caves.

This crumbling stump is all that remains of what was once thought to be the oldest living organism.

A devilishly named gorge that was a sign of salvation for many pioneers.

A monument to the egos of two railroad magnates that fell into decline along with their careers.