Chicago cops found 1,500 pot plants growing inside the city.

Two cops in a helicopter spotted the plants while on their way back to the hanger. It was on a chunk of land the size of two football fields.

There are only a few spots in Chicago where you could grow such a large number of pot plants without being noticed…and the growers hid their crop with a canopy of trees and plants.

Cops think that with such a large number of plants, there must have been quite a few people involved… they're hoping someone will tip them off as to who planted them.

They estimate the weed could be worth about $10million on the street.