If you haven't been to Boulder Creek --- that is the flat spot. The trailer is parked next to an open lot on its right. Big Basin Way is not the main road, it is a side road, so little or no traffic.
PG&E used my riding ring to stage UH-1 lift of a power pole for installation in a park with no vehicle access. I've misplaced my video, unfortunately. The helicopter landed in the riding ring to rig the lift.
my riding ring