The Romans knew from the beginning of its rise as a civilization that a city must have an efficient system of waste disposal in order to grow. Hence, they built in all cities of any importance the sewage systems that still in some cases remain in their original form. In Mérida, for example, the Roman sewer system has been used until recent years, and its design still serves as reference to know what was the layout of the ancient Roman city. In other cities like León (founded as a camp of the Legio VII Gemina) are vestiges of these infrastructures and serve as an example on rainy days of a perfect drainage system to prevent flooded streets .
