Chott el-Djerid

Where it sits. Chott el Djerid is the largest salt pan in the Sahara, a shallow basin roughly 250 kilometres long and up to 70 kilometres wide that spreads across southern Tunisia between the oases of Tozeur and Nefta in the west and Kebili in the east. Parts of the floor lie below sea level. For most of the year it is not a lake at all but a crust of salt and gypsum over grey mud, hard enough in places to drive on and treacherous a few metres away, where a thin lid covers brine and silt. Winter rain and groundwater push a shallow film of water across sections of it; by May that water has gone and the surface has bloomed white again.

What the surface does. The crust is not uniformly white. Iron and magnesium salts, and blooms of halophilic micro-organisms, tint whole sectors pink, ochre and pale violet, and the boundaries between them shift from year to year. Salt crystallises into polygonal plates that curl at the edges and crunch underfoot. Because the surface is flat and hot, the air above it stratifies, and the mirages here are genuinely spectacular: distant palm groves detach and float, and vehicles on the far side of the pan appear to drive through standing water. Caravans crossing the chott historically kept to marked routes, and local accounts of animals and men lost through the crust are a standing feature of the region's oral history.

The sea that was never dug. In the 1870s the French officer François Élie Roudaire proposed cutting a canal from the Gulf of Gabès and flooding the chotts to create an inland Saharan sea, arguing it would change the climate of North Africa. Ferdinand de Lesseps, fresh from Suez, backed the scheme. Surveys then established what the promoters had underestimated: most of the basin, including nearly all of Chott el Djerid, lies above sea level, and the volumes and evaporation rates made the project pointless. The idea was abandoned, resurfaced periodically through the twentieth century, and remains one of the great might-have-beens of colonial engineering.

On screen. In March 1976 the production of the first Star Wars film built the exterior of the Lars homestead on the flat about ten kilometres west of Nefta, at the western end of the chott system. What went up was a domed entrance hut over a sunken courtyard, plaster and fibreglass over a timber and steel frame, with a shallow pit dug beside it. The interiors that match it were shot at Matmata, 250 kilometres away. This is also where the film's most quoted image was made: Luke standing on the rim at dusk while two suns drop toward the horizon, an effect achieved with a single Tunisian sunset and an optically added second disc.

What is left of the dome. The structure was never meant to outlast the shoot, and by the 2000s it was a cracked, sand-scoured shell. In 2012 a group of fans organised an online fundraiser of roughly eleven thousand dollars, hired local craftsmen and spent several days re-rendering and repainting it. That restoration is now more than a decade old and weathering again: the render is chipped, the paintwork is bleached to a pale sand colour, names are scratched into the plaster, and the interior is an empty hemisphere with no fittings whatsoever. It is a stage prop that has outlived its film by half a century, and it reads as one. Visiting it in that spirit is far more rewarding than expecting a preserved set.

Crossing the pan. The P16 causeway, raised on fill across roughly 60 kilometres between Chott el Djerid's northern shore near Tozeur and Kebili, is the practical way to experience the scale of the place. Stalls at the halfway point sell desert roses, the clustered gypsum crystals that form in the sediment, and a few operators keep dyed pools beside the road for photographs. Standing on the causeway shoulder with the pan running to a hazy horizon in both directions is the single strongest impression the Djerid offers.

Getting there and timing. Tozeur is the base; the dome site is reached by an unsurfaced track off the Tozeur-Nefta road and effectively needs a four-wheel drive and a driver who knows the turn, since there is no signage and GPS traces are unreliable after storms. November to March is the window; summer surface temperatures on the crust are punishing and the light is flat and white. There is no shade, no water and no shelter anywhere on the pan, and after heavy rain the causeway itself can close.