I'd like to know, not so much what they explained them as or for, they are historical curiosities that would be interesting to know, but what really motivated groups of people to lay down a plan and organise such huge (and not so huge) investments of time and labour. Why certain structures were more satisfying than the alternatives and replicated over and over, why certain motifs carved in rocks spread across the wildest parts of the Atlantic facade.
I probably wouldn't get the really satisfying answers to these questions by asking the people who were involved, though the stories and explanations they would tell us would be fascinating to record. I'd love to get to the bottom of the part of human nature that drives people to build these things (now as in the past) and what draws us to the abandoned and forgotten sites today.