To reserve the pavillion for a large party you need to pay. It gives you access to the bathrooms in the pavillion at the right side of the park as well. You can go to the office in the park to reserve a date.
I'd call the town of new Hartford to see if they know anything. I don't believe you Need to though seeing as it's a public park.
You do need to reserve, and pay for, the pavilion. You can contact the town of New Hartford Parks dept for costs and availability.
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