Yaxchilan (also sometimes historically referred to by the names Menché and City Lorillard) is an ancient Maya city located on the bank of the Usumacinta River in what is now the state of Chiapas, Mexico. In the Late Classic Period Yaxchilan was one of the most powerful states along the course of the Usumacinta, with Piedras Negras as its major rival.[1] Architectural styles in subordinate sites in the Usumacinta region demonstrate clear differences that mark a clear boundary between the two kingdoms.

http://en.wikipedia.org/wiki/Yaxchilan