The ghout (plural ghitan) is the Souf valley's most ingenious answer to growing food in the Sahara. Rather than irrigate from above, farmers dig vast funnel-shaped craters down to the water table — twenty or thirty metres deep, sometimes more — and plant the date palms at the bottom, where the roots reach the groundwater directly. From above, the landscape around El Oued looks like the surface of the moon: thousands of sandy depressions, each cradling a cluster of palms.
You can see ghouts everywhere on the outskirts of town, but the best views are from the dunes between El Oued and Robbah, where you can look down into the sunken gardens from above. Go in late afternoon when the low sun throws the craters into sharp shadow. Owners are generally happy for you to climb down into a ghout to look, but ask first if you see someone working.