Embalse de La Bolera, Reservoir on the Guadalentín in Jaén Province, Spain

The Embalse de La Bolera is a reservoir on the Guadalentín River next to Pozo Alcón, in Jaén. Its gravity dam has a curved concrete plan, a crest 108 m long at elevation 973 m, and stands 48 m high from the foundations. The reservoir holds 53 hm³ at the normal maximum level and covers 264.55 ha.

Work on the dam began in 1960 and finished in 1978, designed by A. Moreno Torres on the Guadalentín river beside Pozo Alcón. The concrete gravity dam, with a curved plan, rises 48 m from its foundations to a crest at 973 m and holds 53 hm³ at normal maximum level. Its two gated spillways discharge up to 740 m³/s.

The name La Bolera comes from a local tradition: on 9 May, the feast of Saint Gregory, two Jesuit priests were caught in a hailstorm and one carved the IHS monogram and a cross on a stone. That stone was given to the parish of Nuestra Señora de la Encarnación and is carried today in the romería of San Gregorio, alongside an image of the Niño Jesús known as the "Niño de la Bola".

The dam stands in the municipalities of Pozo Alcón, Santiago de la Espada and Cazorla, and the A-326 road crosses the Guadalentín about 200 m downstream at the Puente de la Cerrada. The reservoir is used for fishing, water sports, swimming and irrigation, and the Guadalentín spring and the PB4 cave only appear when the water level is very low.

When the reservoir is very low, the source of the Guadalentín river reappears beneath the surface, and with it the PB4 cave, over 9 km long with three levels and an underground river, flooded when the water is high. Some authors identify this spring with the source of the Tartessos river cited by Stesichorus.