3. Roosevelt Island

Smallpox Hospital on Staten Island
Roosevelt Island‘s Gothic-revival style Smallpox Hospital was completed in 1856 and designed by James Renwick Jr. (who designed St. Patrick’s Cathedral). It was built using labor from the nearby lunatic asylum. It functioned for 19 years and treated about 7000 patients. Many of these were impoverished immigrants who  had not received the vaccine yet or didn’t trust the immunization process, or Union soldiers who needed curing.
In 1875, the hospital closed when it became too crowded and the facilities were relocated North Brother Island. Remarkably however, the original building remains today and is the only landmarked ruin in New York City. You can see this hospital on your way to Four Freedoms Park.