NYC has plenty of secret areas to grow in, but one spot that really tops them all is the water tower gro-op.  All over the skyline are abandoned towers that Nuggs sneaks into and starts building indoor operations.  Each one can take a couple months, but be ready once completed.  Every cycle is guaranteed to produce up to 10 LBS a run, giving you plenty of room for harvesting and trimming.  

With your gro-op so high in the city sky line, being on the lookout for scavengers and "popo" becomes much easier.          

Standing about 16 inches tall made with various materials