In San Juan ’s hot, arid climate, the vineyards thrive on water from 3,200-hectare Dique Ullum, 18 kilometers west of town via RP 60; it’s also the place where Sanjuaninos go to beat the heat by swimming, sailing, windsurfing, and fishing. From the bus terminal, take bus No. 23 to Zonda; for schedules, contact Empresa Ullum (tel. 0264/422-1910).
If the heat relents, hike from the dam outlet to the top of 1,800-meter Cerro Tres Marías. This waterless walk traces the crest of the southwest-trending Serranía de Marquesado and takes two hours one-way. The conspicuous zigzag trail begins at the Stations of the Cross; carry plenty of liquids and high-energy snacks.