Several dozen fresh- and salt-water (brine) springs emerge from the rocks to form a series of waterfalls at Oum Er Rbia, and the river cascades down the mountainside. Along the banks are simple bamboo cabins with cushions and tables that you can rent (per day Dh100). Above them are makeshift cafes that supply mint tea and tajines to order. It's too dangerous to swim, but locals love to spend the day here, relaxing in the cabins surrounded by magnificent scenery.
The river forms the boundary between the Ifrane and the Aguelmam Azigza National Parks. The road south from Ain Leuh climbs through cedar forests and deteriorates at some points, but the vistas are superb; expect the 33km drive to take about an hour. The car park is busy at all times; weekends are particularly congested. There's a Dh2 charge to use the toilets.
From Azrou, it costs a hefty Dh1200 to hire a private grand taxi for this trip (including a stop in Ain Leuh), but the springs are also included in some Middle Atlas tours. From Ain Leuh, the road ascends through thick juniper, oak and cedar forests, where troops of Barbary macaques are sometimes spotted, and skirts tiny Amazigh communities. Watch out for shepherds and their flocks, nomad settlements in summer and working donkeys going about their daily tasks.
It's also possible to hike to the Oum Er Rbia springs from one of the region's lakes: leave the road at Lac Ouiouane, about 20km south of Ain Leuh, and follow the path down past a number of farmhouses to a small valley, where a bridge crosses the Er Rbia River. From here, it’s about a 15-minute walk to the gorge and its cascades. In total this trail will take you about three hours (approximately 10km).