Not sure exact location. I took off from the farthest west field in the default country (the farthest east country?) and flew southwest towards where the two opposing V fields are right next to each other. A little bit before the V fields and eastish of where those hills start, I noticed what looked like slivers of gray terrain tearing. Going lower and flying near them revealed they were a completely different texture and there was a ramp going down, a short tunnel area, and a ramp going back up. The ramps were terrain green, the walls of the ramp and ceiling of the tunnel area was a grayish structural stone tile texture. There were a couple of these tunnels in the area, possibly to enhance vehicle combat as they were near those 2 V fields.
