Cornalvo Reservoir is located about 10 km from the city of Merida, in the autonomous community of Extremadura, Spain. The reservoir capacity is estimated at 11 hm3.1 The dam is a Roman building on Albarregas stream, which was used to supply water from the city of Emerita Augusta (now Mérida). Containment is a solid wall of 220 m long and 18 m in height, while the part that is in contact with water in the form of terraces. The work is dated to the year 130 A.D.. The designer is unknown. This building was declared a National Monument on December 13, 1912. The reservoir is still used today. All your environment is a natural park, so it enjoys special protection of Extremadura since 1988. It has a rich flora and fauna in the park entrance we find an interpretation center that will help us in the visit.