The beauty of urban decay, hiding some dark secrets.

A crumbling hospital from the 1850s on Roosevelt Island.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.

America's oldest archaeological site or a muddled case of wishful thinking.

Once the most densely populated place in the world, this island is now a ghost town.

Steam engines and conveyor belts are remnants of a genius system left in the middle of the Maine woods.

17th century streets hidden under Edinburgh were once a breeding ground for the black death.

This notorious Canadian mental institution was home to some of the first LSD experiments and origin of the word "psychedelic."

The inspiration for H.P. Lovecraft's horror stories and Batman's Arkham Asylum is now a condominium complex.

The ancient tomb acts as a calendar that keeps perfect time.

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

The ghost town left by the worst nuclear disaster of all time is being taken over by nature and urban explorers.

Venice's "Island of the Mad."

A museum devoted to bringing to light forgotten or neglected histories through exhibitions, education and public programming.

The history of the treatment of mental illness, illustrated in all its gory detail, and housed in an asylum.

A Museum of Psychiatry in a still-operating mental institution.

A treasure trove of pathological, forensic, parasitological, and anatomical specimens.

This Boston medical museum features the skull of the famous medical case of Phineas Gage.

Anatomical cabinet holds unexpected treasures.

Contains some of the world's more disturbing wax anatomical models.

A unrivaled and rather horrifying collection of wax dermatological models.

America's first public mental health facility.

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