If you don't mind me answering a question with a question.
What makes you believe categorically that these structures are tombs?
I personally have no idea what their purpose was, not enough evidence to say one way or the other.
I could guess or believe that they are tombs, but that's mere guesswork and belief.
Edited 1 time(s). Last edit at 06-Feb-16 19:16 by Jon Ellison.