A tiny microvalley etched into the side of Knocknarea Mountain hides another world.

This strange example of the Egyptian Revival architecture trend now holds Mardi Gras floats.

This New Orleans tree is filled with hidden chimes that produce a carefully tuned melody.

The final resting place of New Orleans' most famous voodoo priestess.

Tiny historical streetcars wind through a small scale version of Crescent City in this whimsical train garden.

This stately building in Alexandria, Virginia was built by Freemasons to honor one of their most famous members.

An eccentric company offers eccentric millionaires the opportunity to have spaceflight-related experiences.

The rogue roots are gradually consuming some of the historic marble grave markers.

Soldiers were buried next to Lee's house in the center of Arlington Cemetery to dissuade the general from reclaiming his property after the war.

The controversial urban planner who designed Washington, D.C., was buried in Maryland, and can presently be found in Virginia.

The naval commander’s proudest moment in battle is memorialized in this unique tomb at Arlington Cemetery.

A double agent hid information for the Soviet Union beneath this bridge for more than 20 years.

This grave marks the passing of a historic Jane Doe whose identity remains a mystery to this day.

An extensive, if one-sided, history of U.S. law enforcement's war on drugs.

This forgotten boat elevator was an engineering marvel in its heyday.

The Pentagon is so large that it was planned like a city, complete with internal highway infrastructure.

This unique historical monument features large concrete spheres designed to resemble fallen stars.

Parking garage where Bob Woodward met Watergate source "Deep Throat."

Rumor has it the hot dog stand was targeted by two Russian nuclear missiles.

The national park was once a plantation estate.

A wondrous old library overlooking the nation's capital.

The site of the climactic scene from the classic horror film is now a historic landmark.

Before Metro, Washington had a robust streetcar network—and you see the remains of this infrastructure if you know where to look.

These abandoned waterworks are crumbling into the Potomac River.