The mouth of this great canyon is located in the State of Queretaro. It is the most spectacular in the central part of the country. Its length is 180 kms with walls running up to 480 Mts. in certain parts. The rivers Tula and Moctezuma run through here for 12 kms. In the mouth of the canyon is the hydroelectric plant of "Zimpán", whose dam has been built 100 mts inside the canyon. This wall 200 mts high forms a damming that fills up part of the basin and valley of the San Juan and the Tula Rivers.