One of the most influential presidents in U.S. history wanted only this plain, elegant monument as his lasting memorial.

This rare triple-jurisdiction drawbridge passes through Virginia, Maryland, and Washington, D.C.

This lovely picnic spot featuring thunderous jet landings is an aircraft spotter’s dream.

The historic home still shows the scars from a little run-in with the British in 1813.

Washington's iconic carousel has a nice piece of Civil Rights history.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

The site of the one of the most deadly train wrecks in American history.

The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.

These abandoned waterworks are crumbling into the Potomac River.

The stone marker that Mason and Dixon placed at the eastern end of the famous north-south border they surveyed.

The first American home of the isolated, egalitarian religion has a trove of Shaker architecture and artifacts.

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

Before founding the American Red Cross, Clara Barton had a tremendous humanitarian impact by locating thousands of missing soldiers.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

Strange red rock formations that have been attributed to a higher power for hundreds of years.

This historic "City of the Dead" lies prominently in the center of New Orleans' famous Garden District.

See massive fossils that are over 200 million years old in northeastern Arizona.

Quite simply the largest tree in the world (by volume).

Trails through lava-carved tube-caves display sparkling bacteria and a rich history.

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

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

A museum dedicated to the alleged Roswell Incident.

The trials and tribulations of marking Poe's grave.

A pedestrian island in the middle of world-famous Times Square emits a strange (and purposeful) humming noise.