The Ancient Walls: Enigma in the Andes
   A slideshow of Andean archaeological sites by Richard Nisbet with a focus on Inca architecture and stonecutting. He suggests that the lower structure of Sacsahuaman is much older than c.1508.
   http://home.earthlink.net/~rnisbet/indexwalls.html

World Mysteries: Sacsayhuaman
   Describes several Inca sites in Peru, with some speculation about alternative dating.
   http://www.world-mysteries.com/mpl_9.htm