Nine of the very few concrete ships ever made in the U.S. are beautifully decaying off a Virginia pier.

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

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

After hundreds of years of settlement, this once-bustling fishing village sunk into the Chesapeake Bay.

The abandoned ruins of a failed resort hide on this verdant, picture-perfect island.

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

There’s a special club house at the top for the bell ringers.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

An Industrial Revolution-era public work that purified water using nothing but sand.

A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

Hidden in a grotto 26 feet below Nottingham's oldest hotel, this stylish subterranean drinking den is notoriously hard to find.

A historic neighborhood church is reborn as a psychedelic arts collective.

The national park was once a plantation estate.

People escaping slavery may have hidden inside a corpse vault.

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

The winding route passes through an enclosed alleyway, two tunnels, and leads to the White House basement.

A building shaped like the Army Corps of Engineers logo, because why not?

A rotating cast of guys and dolls in front of a Washington, D.C. building.

Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

Home to a vast and influential collection of Shakespeareana.

Beautiful stained glass depictions of the history of human flight fill this surprising chapel.

Memorial built in 1922 in remembrance of WWI casualties.

The remains of an old sawmill, gristmill and the surrounding industry dating back to the 18th century.