What are these circles?
Farms. Some fields are more easily manages in circle rather than fully square edges
Theyr'e the patterns made by field irrigators that rotate around a central point.
Farmers using rotating irrigation booms
Center point irrigation systems
https://en.m.wikipedia.org/wiki/Center-pivot_irrigation
https://en.wikipedia.org/wiki/Center-pivot_irrigation
Farms. Some fields are more easily manages in circle rather than fully square edges