El Hoyo is a volcanic complex consisting of several volcanic structures. The first volcano in this area was called El Picacho. After being active the volcano collapsed, and several other volcanic structures were formed. Nowadays, the most significant structure is the El Hoyo Volcano. This volcano can be easily recognized by the huge hole located on a slope of the volcano. Climbing the volcano is possible but not often done. The area is located in a sparsely populated area, and there are no roads to the base of the volcano. It is easiest to reach the foot of the volcano by horse.
Other volcanic structures include the Las Pilas volcano, another stratovolcano just like El Hoyo, and two maars called Laguna Asososca and Malpaisillo. Maars are flat craters formed after a violent eruption. Water often collects in these craters, forming a crater lake. The Asososca Lagoon is completely filled with water, and part of the Malpaisillo maar is also filled with water.