The crowd on hand to see Snowden and Ellsberg was insane, to put it mildly. The conference had taken over the entire 18th floor of the Hotel Pennsylvania for the event, which took place in the main hall and was broadcast via closed circuit to all the other rooms.
The 18th floor was closed to further traffic due to overcrowding about an hour before the event began, and re-directed to the 6th floor. The 6th floor also quickly filled up, and the first floor and mezzanine became the overflow rooms. By the time the event actually started there were people spilling out onto the street trying to see what was happening.