Really big mountain that overloooks Mexico City. In fact, it is a volcano. Close to it stands the Iztaccihuatl, another volcano. The Popocatepetl is locally known as Popo and also Don Goyo.
As I write this node, it is erupting.

The Popocatépetl reaches an altitude of about 5420 m, and in good days it looks very impressive from Mexico City. There is a very small and receding glacier close to the tip. It stands at 19°03' N and 98°35' W. Closest major urban centers are Puebla, Cuernavaca and Mexico City. There are many small villages between 10 and 20 km. from the crater

Standard access to the mountain is through the Paso de Cortés and Amecameca.

You can see a picture of Popo at (during daytime).