Topo map of Nevado de Toluca...

Topo map of Nevado de Toluca showing peaks of the crater rim and the approach trail from the state-run hut (dashed black line). The hut is located at the point designated "Est Meteorologica." The easiest route to Pico de Fraile begins outside of the crater at the hairpin turn in the road just before the snow line. It ascends to the saddle between the crater rim and Cerro Prieto and then follows the ridge to the crater rim and on to the summit. Picture from http://www.xpmexico.com.