The dunes begin almost at the edge of Khamlia, which gives the village an advantage over the busier resort strip around Merzouga: you can walk straight in from the village rather than having to negotiate quad bikes and camel touts. The dunes are enormous — walking from the base to the crest of the main ridge takes a fit person around 45 minutes, and the view from the top extends to Algeria on a clear day. Go at dawn if you can manage it; the light is extraordinary, the air is cool, and the footprints from the previous day have already been erased by overnight wind.
Camels are available through local guesthouses for those who prefer not to walk. A short camel ride to a bivouac and back is one of the standard Sahara experiences; if you want the full version — sleeping under the stars in a proper tent camp among the dunes — it is worth arranging in advance rather than on the day. The dunes are at their most spectacular in late autumn and winter when the heat is bearable and the sky is reliably clear.