Altar de Sacrificios is located in Guatemala

Altar de Sacrificios is a ceremonial center and archaeological site of the pre-Columbian Maya civilization, situated near the confluence of the Pasión and Salinas Rivers (where they combine to form the Usumacinta River), in the present-day department of Petén, Guatemala. Along with Seibal and Dos Pilas, Altar de Sacrificios is one of the better-known and most intensively-excavated sites in the region, although the site itself does not seem to have been a major political force in the Late Classic period.

• http://en.wikipedia.org/wiki/Altar de Sacrificios
• Page 168 - Hunt, P., 2007, Ten Discoveries that Rewrote History: Penguin, New York, 226p.