The basin of the River Los Molinos are limited to the west for the Pampas and Summit of Achala; to the east, for the cords of the Small Mountains; to the north for the Mountain or Cord of Santiago that it separates the Valley of Punilla of that of Santa Ana (where it is the reservoir); to the south, a continuation of the summit of Achala separates it of the Valley of Calamuchita.

The basin of the River Los Molinos are constituted by the rivers San Pedro, of the Espinillos, del Medio and of Los Reartes and their respective ones flowing.

It is developed in a rural landscape, with strong slopes that have allowed the intense erosion carried out by their tributaries when descending from the oriental border of the Pampas and Summit of Achala until reaching the bottom of the valley.

The Prey Los Molinos have as basic purposes the supply of water for potabilizar and it stops watering, the electric power generation (The Power station Los Molinos I produces 148 millions of Kw. per year) and the attention of grown. It was built between 1948 and 1953 first floor the address and idea of the Engineer Fitz Simón. It dams the waters of a basin of feeding of 980 square kilometers.

The civil work possesses a height 60 meters and a longitude of crowning 240 meters . Other technical data give bill of a bench mark of 769 msnm., a surface of 2451 hectares and a volume of 399 cubic hectómetros.

The mark of this engineering work is framed by a flora and wonderful fauna. The vegetation according to the altitude is represented by floors: mountain forest (molle, coconut, pruning and espinillo), arbustal or romerillal (romerillo, carqueja and tiger beard) and pastizal of height (gramineous). The coniferous ones that can be admired were introduced from 1940.

The fauna observable includes foxes, zorrinos, weasels, vizcachas and hares. We will be surprised biguás, blue, jotes, shielded eagles, partridges, larks, thrushes and kingfisher fisherman. According to the time of the year iguanas, small lizards and big and small yararás can appear. The lovers of the fishing will discover pejerreyes, eels, bagres, trouts and carps.

The main human activities of the region are sustained in the Tourism, for adventurers that love the rural thing until those that prefer centers urbanized with all the services like General Villa Belgrano, Santa Rosa and Alta Gracia. They also stay with the cattle and forest exploitation, and unirrigated land cultivations.