Anasazi's Master Builders

The largest of the Anasazi kivas was a little over 60 feet in diameter. The double ringed circles in Area 51 and California are approximately 60 feet in diameter. The eroded circles near the water areas are a bit smaller and do not have double rings and could possibly be some type of plant mound but I'm still uncertain why they wouldn't be more widespread... I wish it were possible to go take a close-up look.