Seen quite a lot in many fields in Idaho, Wyoming, South Dakota (it will be there in other states too).The thin strings hanging down are the sprinklers (in action in the photo) and there will be a water gun at the end too (the end gun is not in action in this photo). Some of them are very very long (radius/diameter)… Wikipedia says most common size (diameter) is 1/2 mile (or 0.8 KM) which will cover irrigation of 125 Acre land. I think we saw many such big ones during the trip..