On the construction of megalithic architecture? On their use? Symbolism?

If you are interested in the construction part of it, I can be of some use. I study architectural energetics and labor organization. Energetics is the quantification of labor in order to better understand how many people and how much effort was put into constructing things like palaces, roads, terraces, pyramids, etc. I can direct you towards some of the key research on this topic.