Dique El Cajón, officially known as Embalse Heralio Argañaraz, is a reservoir situated in the Valle de Punilla in the Sierras de Córdoba, approximately 1 kilometer from the center of Capilla del Monte, at an elevation of 910 meters above sea level. It sits along Ruta Nacional 38, between Capilla del Monte and San Marcos Sierras in the northern part of the Departamento Punilla. The dam impounds the Río Dolores within a natural canyon from which the reservoir takes its name — "El Cajón del Río." The dam wall is 39 meters tall with a crest length of 67 meters, and the reservoir covers a surface area of 1.45 to 1.8 square kilometers with a water volume ranging from 8 to 12 cubic hectometers. The surrounding landscape features prominent pink granite formations and mountain terrain.

Motorized navigation is not permitted on the reservoir. Permitted water activities include kayaking, sailing, windsurfing, and canoeing, making it a calm, non-motorized paddling environment. The water depth ranges from approximately 5 meters near the shore to 30 meters at the center of the reservoir, which is relevant for paddlers assessing conditions and safety margins.

The dam wall can be walked across on foot, and the Camino del Perilago follows the shoreline. Facilities in the area include Playa Grande, the Balneario Águila Blanca, and a fishing club. The eastern shore features a historic structure known locally as the "tapera" associated with Argentine actor Enrique Muiño. The reservoir is also used for fishing, primarily pejerrey and carpa, so paddlers should expect fishing boats and anglers sharing the water.

The reservoir is visible from the summit of Cerro Uritorco, one of the notable landmarks in the area. Other nearby points of interest include El Zapato, Los Terrones, La Toma, and El Paso del Indio. The dam was constructed between 1987 and 1993 and serves multiple purposes: drinking water supply, irrigation for San Marcos Sierras, flood regulation of the Río Dolores, and recreation.