Welcome to the Park Avenue Malls. Though the middle of Park Avenue may seem like a bad place to get away from the hustle and bustle of the city, this small "island" of green is actually a peaceful place to relax, eat lunch, or observe MNR Hudson Line trains as they enter and exit a tunnel beneath your feet. Maybe you'll spot one during your visit!
GPS signal in Manhattan can be bouncy because of tall buildings, so here's some advice to locate the cache: As you reach north end of the island, face the train tracks and find the closest bench to the street on the left side of the circle.
As always, please remember to seal the container properly and replace it as (or better than) you found it for the next cacher to enjoy. Also, as park hours are sunrise to 1AM, the cache is only available during those hours. BYOP!