Copan: Tunnels [January 9, 2004]
"Individual structures enjoyed almost continuous rebuilding and refurbishment, and much of the Acropolis was transformed by at least two major renewal/construction projects between ca. 500 and 650, a time corresponding roughly to the reigns of the fifth through the eleventh rulers. Significant structures dated to this period include a major two-tiered platform on the eastern side of the East Court, decorated on all four sides with large plaster and painted masks."
Robert Sharer, The Ancient Maya, p. 311