London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

The oldest continuously operating fish market in the United States.

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

A derelict bit of transportation infrastructure hidden in the woods.

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

A Spiritualist house of worship where believers communicate with the dead in the spirit world.

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

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

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

Once home to seven different roller coasters, Glen Echo has undergone many transformations since its founding in 1891.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

There's a crumbling old mansion inside the Smithsonian National Zoo.

A celebrity from the late Cretaceous period.

The United States Capitol's former columns still stand.

The towering figures were created from the cemetery's fallen old-growth trees.

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

Cold War intelligence agents monitored communist embassies from an attic in a former pigeon coop.

Once the supplier for noteworthy projects like the National Cathedral, this old brickworks now lies abandoned.

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.

The shelves in the back of this thrift store are devoted to saving, not selling, retro tech.

A benevolent, 16-foot-tall river dragon lives on a suburban lawn.