Is this a water tank on Mount Davis? This one locates in the lower southwestern area. Looks likr someone had a lovely day here.
Another tank-like thing is on top, which has an iron shield on its top and a small hole in the center. Was thrilled when looking through that center hole when immediately saw my own face in the bottom. Seconds later recognized there is water inside it. The location is clear on the map.
Maybe the top one is an anti-aircraft silo.