I have some questions with regard to Stonehenge's so called "Altar Stone"?
1/ Can the Altar Stone at a certain point have been on top of the lintel of the great trilithon? Could this account for its current location? Are there arguments which completely undermine this possibility? The upper lintel has small mortises on its upper side. I know there are several unusual things about tenons and mortises at other locations at Stonehenge. Sometimes, some authors advance explanations for it.
2/ According to many, the Altar Stone was a recumbent stone. I do not know if this possibility can be really undermined. The inner space of the sarsen horseshoe especially could have functioned at certain times as a livestock market (maybe with wooden structures added). If that was the case, maybe part of the personnel was behind the altar stone. The altar stone could even have been used as a kind of bar after such an event. I read a lot of things about ceremonies at that time, but what about sheer leisure, games, etc.? It is well known, e.g., that in Native American societies many adult men spent a lot of time playing ball games. This second option (a bar after working hours) may appear as a joke at a first reading, but things like that could also produce richness (a.o., by attracting clients to buy or sell cattle, reenforce human relations, etc.), richness being the most important goal of a great deal of people in really many societies and cultures.
(Hypothesis 1/ has of course nothing to do with 2/)