Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

A former major munitions plant that has been converted into a sprawling art space.

This isn't your average roadway—it's actually a National Park and a transportation pioneer.

One street divides a single town that stands in two U.S. states.

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

The first declared National Monument in the United States.

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.

A unique geological area spiked with wind-carved rocks that resemble teepees.

Despite time, colonization, and the brutal New Mexican heat, these Pueblo ruins still stand.

A small metropolis of Pueblo cave dwellings have been carved right into the hillside of this national monument.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

A museum dedicated to the alleged Roswell Incident.

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

Once America's tallest structure, now a Baltimore landmark.

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

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

A blank headstone topped with a pile of pennies marks the final resting place of the infamous assassin.

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

Experience the hysteria of a 17th century witch hunt through goofy reenactments and wax dummies that should probably be burned at the stake.

The oldest continuously operating fish market in the United States.

An obscure federal monument honors the French diplomat who served as Ambassador to the U.S. during WWI.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

The Byzantine, pre-Columbian, and medieval art at this stately mansion are some of the most under-appreciated collections in D.C.

The most accurate timepiece in the world.