America's original house of worship for Spiritualism, the religious movement based on communing with the dead.

American revolutionaries and British soldiers alike are buried here in the fourth-ever cemetery in Boston.

The oldest working bell set in North America, the bells at Old North Church sat silent for their first four years in Massachusetts.

The Boston square dedicated to the dark poet who was born nearby.

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

Baltimore's classic clock tower was once topped by a rotating, 20-ton medicine bottle.

This huge clock made of flowers and simple machinery was once used a political weapon.

One of the only known surviving coconut palm trees in the entire state.

After starting as a whimsical tourist attraction that eventually found its way to ruin, these renovated canals offer a lush and exotic locale on the Pacific Coast.

An abandoned facility that has become a place of ritualistic satanic worship, or so rumor has it.

The sculptor was instructed to add “stallion attributes” to the general's bronze mare.

A bas relief commemorates the "Nuns of the Battlefield" who cared for soldiers on both sides of the conflict.

The walls of the iconic dome are hollow and have a secret stairway.

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

The seamy, underground secrets of Portland's criminal past.

There’s a hidden military meme engraved on the World War II Memorial.

This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.

The monument's pointy aluminum tip has been melted down by repeated lightning strikes.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

Color-coded signs direct drivers on a network of routes designed to avoid Pittsburgh traffic.

A sculpture of a salmon swimming through a brick building.

It was once the base for a series of domestic terror attacks.

This Manhattan skyscraper is a reminder of the brief but glorious age of urban air taxis.