Home to items never before seen by the public.

This huge, disused viaduct is now a crumbling concrete underworld of covered in years of graffiti.

Philadelphia boasts one of the best — and most often overlooked — traditional Japanese gardens in North America.

Arlington Cemetery exhibit dedicated to death and grieving.

Salute the leader of the proletariat.

The feral felines of Roosevelt Island have a small army of allies and an abandoned hospital all to themselves.

A crumbling hospital from the 1850s on Roosevelt Island.

The headquarters in Salem doubles as an occult art gallery.

This historic iron-working village is now a ghost town so immaculate that it looks as though it was recently built.

A recently abandoned psych ward at the end of Sanatorium Road.

These beautiful ruins deep in the Pennsylvania woods are thought to have been a ski lodge or a speakeasy, but no one really knows.

An ideal wedding spot that is almost too ideal.

The final resting place of the Hollywood star who came to a tragic end.

A field of nothing but boulders which resembles a giant's gravel driveway.

Enjoy a slice while browsing the world's largest collection of pizza memorabilia.

A clone-tree in Washington Square Park sprung from seeds that went to the Moon and back.

A layered tribute to the work of mosaicist Isaiah Zagar.

Huge masonic hall in Philadelphia with lavishly themed rooms.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

Dr Barnes' $25 billion private collection of art and arboretum.

World's first "penitentiary," meant to be humane, drove men insane.

The oldest surviving botanic garden in the United States.

Pennsylvanian mass grave and possibly mass murder.

This hidden gem of a garden has one of the only surviving Victorian ferneries in America.