Tightly packed kivas. Some have tunnels to each other, some are stand alone. The hard part about trying to figure out how they were used is that religion tends to make people behave in patterns that are are difficult to reason out. Imagine digging up the foundation of a local church: how much could you deduce from the sterile bricks that are left behind? There are no hints of the ceremony, no clues as to why there was a main entrance and smaller exits at the other end.