Siwa lies nineteen metres below sea level, and that is the reason it exists: some two hundred springs push up through the floor of the hollow. The oasis sits in Egypt's Western Desert, far enough out that its people still speak Siwi, a Berber language kept nowhere else, and the water carries 280,000 date palms. On the rock of Aghurmi stands the temple of the oracle of Amun, which Alexander crossed the desert to consult in 331 BC. It told him he was the son of a god. Below it the old town of Shali was built from blocks of clay so salted they set like cement — and melt in rain. Three days of it were enough. What climbs the rock now is a soft, half-dissolved stump of a town, and the lanes still take you up to a top where the palm groves run out to the dunes closing the horizon.
A round stone pool bubbles up under the palms at the edge of the gardens, deep enough to swim in and busy with local men all afternoon. Herodotus described this spring as cool at noon and boiling at midnight. In fact it holds nearly the same temperature all day; what changes is the air around you. East of town, pits cut by a working salt quarry hold brine heavy enough to carry you like a plank, over crystal shelves that crunch underfoot. Past the last garden wall the Great Sand Sea begins and runs unbroken for hundreds of kilometres. Drivers take you over the crests and down the slip faces, and the nights out there are as dark as Egyptian skies get. West of town a palm causeway runs across Birket Siwa to Fatnas Island, and at sunset the water goes flat and metallic while the palms cut to black. But the springs work both ways. Unused water and field runoff keep pouring into those salt lakes, lifting the water table and salting the ground, and the lake half the town walks out to at sunset is nearly three times the size it was thirty years ago.