Tucked away on a deserted island are the crumbling ruins of the most haunted place in New York City. Renwick Smallpox Hospital, which eventually became the Maternity and Charity Hospital Training School, opened its doors in 1856 but was abandoned a century later leaving only the ghosts behind.

Designed by York & Sawyer, the three-story, U-shaped Neo-Gothic building looked out across the underdeveloped southern tip of what was then called Blackwell Island. The distance between the island and NYC made it a perfect quarantine area for patients infected with smallpox, many of whom were newly arriving immigrants.

The 100-bed hospital treated 7,000 patients annually, and roughly 450  would die each year. That means that upwards of 13.5 thousand deaths due to smallpox happened within the walls of the Renwick during its 30 years as a hospital.

In 1886, two extra wings were added to the original block structure and the Renwick became a training hospital and teaching facility for nurses. Finally, in 1973, the island was officially renamed Roosevelt Island, and the Renwick Ruins were abandoned completely. At the same time, the hospital became the only ruins in the city to be deemed a historic landmark.

Since then, there have been many restoration projects set in place in order to keep the building intact. In 2009, a $4.5 million stabilization plan was put into effect in order to open what was left of the hospital to the public. After the initial restoration, the hospital was illuminated at night, and now guests are able explore the paved walkways that surround the ruins.

Not much is left of the inside of the building but crumbling floors and rotten stairwells. Luckily, the outer framework was salvaged, and today a gate surrounds and protects the hospital to keep people from getting too close.

Many who've visited the hospital report experiencing strange sounds, lights, and even dark shadows that seem to watch you from behind the looming walls. When you consider the amount of death that occurred inside the building, it's no surprise that many visitors report having their own first-hand experiences with spirits at the Renwick Smallpox Hospital.

If you're interested in seeing the building for yourself and possibly having a paranormal encounter of your very own, visitors are able to explore what's left of the abandoned structure from a safe distance.

Plan your own supernatural road trip this summer with this hand-curated guide to the most terrifying haunted locations all across America. Just don't forget to bring your flashlight!

Renwick Smallpox Hospital is NYC's most haunted historical landmark

Renwick Smallpox Hospital is NYC's most haunted historical landmark

Renwick Smallpox Hospital is NYC's most haunted historical landmark

Renwick Smallpox Hospital is NYC's most haunted historical landmark

Renwick Smallpox Hospital is NYC's most haunted historical landmark