Town parks often have man made ponds.
This one is a reservoir, created in 1948 by building a dam across a stream, resulting in a body of water of about 60 acres. The inflow is from other small brooks in the north end, including one that seems to originate in a bigger pond a little ways north (that pond also has a dam, so I don't think fish come down from that one: the northern pond has big pike, the reservoir has none). The town does stock the reservoir with brook and rainbow trout, but I don't know how frequently. There are good size bass in there, up to at least 5 lb (you Floridians can stop chuckling). I don't know where the bass came from, supposedly they don't stock those (maybe a long time ago). Speaking of stocking, my understanding is that since it is a town resource, and you have to buy a town pass to park there (and only town residents can do so), the state doesn't stock it and the town has to do that.
I have caught LMB, SMB, crappies, brook trout, golden shiners, and millions of bluegills in there (it is a great place to take kids fishing since you can reliably catch as many bluegills as you want, practically on a bare hook). No koi yet though! (Since I do catch and release, I am really not planning to go after that guy.)