(AFAIK)They where there to celebrate the passover meal. They could not find a place to have the meal, every place was booked,so the upper room was probably a roof top. Thats what I heard on the street. The had no idea that the incredible significance of what was about to go down. JC of course was finally laying it all down. The grail was a hand thrown mud cup, and just like most of the gospels the story grew a life of its own. But all that does not matter. What matter is what Jesus means to you personally. just my opinion.
"You were not there for the beginning. You will not be there for the end. Your knowledge of what is going on can only be superficial and relative" William S. Burroughs