Citlaltépetl
It is located at an altitude of 4850 meters on top of the Sierra Negra, the fifth highest peak in Mexico and an extinct volcanic companion to Mexico's highest mountain, the Pico de Orizaba, inside the National Park Pico de Orizaba in the state of Puebla. It is a binational Mexican (70%) – American (30%) joint project of the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE) and the University of Massachusetts Amherst.