Our Passover liturgy from a couple of years ago - http://markjberry.blogs.com/.m/passover_meal.pdf
And a picture showing the Kataluma - the upper or guest room. Incidentally according to Paula Gooder (who I'm listening to as I post) this "Kataluma" is the word which has been mis-translated into "inn" in the Nativity story, note it is the pace of hospitality, where guests would stay and which was full at the time of Jesus birth so he was born underneath it in the animals space. Yet when the time came for the Pesach, his last Passover feast there was room. It was not a room as such but an open roof top with a cover made from palm leaves. I can imagine therefore the lights, noise and prayers from Katluma all over the city merging into one... Perhaps the "last supper" was a far more public event than we imagine... Maybe when Jesus strayed from the Seder ritual suddenly this one party was out of sink with those around?