Los Reyunos is a reservoir on the Río Diamante in central Mendoza Province, approximately 35 kilometers from the city of San Rafael. The dam that forms it stands 130 meters high and was constructed of stone and compacted clay. The reservoir covers an area of 7.40 square kilometers. A smaller compensation dam called El Tigre sits roughly two kilometers downstream, forming a lower reservoir used in conjunction with the pumped-storage hydroelectric system; water is periodically pumped back up from El Tigre into Los Reyunos to stabilize the main reservoir's level, which is a factor paddlers should be aware of when planning trips.

The water displays distinctive green and turquoise tones, and the reservoir sits within a mountain landscape. The shoreline terrain includes rocky slopes typical of the Andean foothills of Mendoza.

Paddling rentals are available through at least two operators at the reservoir, including Club Hidyn Los Reyunos and REYUN Aventuras, offering kayaks, canoes, stand-up paddleboards, and pedal boats. The Club de Náutica y Pesca Los Reyunos also provides boat tours and sport fishing, and operates camping and accommodation facilities on site. Safety instructions and equipment are provided upon arrival at rental operations, and the use of life jackets is recommended for anyone entering the water.

The reservoir also hosts motorized water sports including water skiing, wakeboard, and windsurfing. In March, Los Reyunos serves as the venue for the Argentine Wakeboard Championship, which draws competitors nationally. Paddlers sharing the water with motorized craft should factor this into their planning, particularly during peak summer and event periods. A recorded kayak route on the reservoir covers approximately 3.7 kilometers with around 51 meters of elevation gain, taking roughly 53 minutes to complete.

The area around the reservoir supports additional activities such as horseback riding and rafting, and native chinchillas have been reported near the shoreline. The reservoir operates year-round as a tourist destination, with activities available across all seasons.