A stone monolith carved with a representation of Tlaltecuhtli, the Aztec god of the earth, is seen in Mexico City, in this Thursday, Nov. 16, 2006, file photo. Mexican archaeologists, using ground-penetrating radar, have detected directly below the monolith, underground chambers they believe contain the remains of Emperor Ahuizotl, who ruled the Aztecs when Columbus landed in the New World. Credit: AP Photo/Eduardo Verdugo