If you’ve ever jogged or strolled around Gramercy Park, you’ve probably peeked through its fence, and stared longingly at the green foliage inside. Located in the Gramercy Park Historic District, the 2-acre private green space is fenced-in all around, and only those with keys are granted access inside. As one of only private parks in New York City (and one of three in the state), it’s shrouded in mystery, leaving many New Yorkers intrigued.

10. Gramercy Park Arose out of a Swamp

Although Gramercy Park is covered in trees now, it actually sits in the middle of what used to be a swamp. In 1831, real estate developer Samuel B. Ruggles purchased the property from James Chatham Duane (the son of the former mayor, James Duane) with the intention of transforming it into an open green space. Because it was so full of puddles, he spent $180,000 draining the marsh and landscaping the grounds, which was known as Gramercy Farm at the time. Ruggles, who was also instrumental in constructing Union Square, played an important role in laying out the housing that surrounds the park.