Liwa is a crescent of date oases a hundred kilometres long on the rim of the Empty Quarter, the largest continuous sand desert on Earth, and the only reason anyone could live out here is underground. An aquifer beneath the sand feeds the palms, and the palms fed the Bani Yas, whose ruling family founded Abu Dhabi and moved to the coast. You can step off the sand straight into one of the gardens, where water drawn from that aquifer keeps the ground green a few metres from an ocean of dunes. The dunes themselves are not quite the colour they look. Each pale quartz grain wears a thin coat of iron oxide, picked up over thousands of years of tumbling, so the oldest, least disturbed sand runs deepest red and freshly shifted grains stay pale. The ridges are the work of the shamal, the northwesterly off the Gulf, which drives them into long lines at right angles to itself.
Moreeb is the country's tallest dune, and its fame rests on pitch rather than height: a face reported past 50 degrees. You wax a board, walk to the lip and drop in with the sand hissing under it. The ride lasts seconds; the climb back up through ground that gives way underfoot is the part nobody photographs. Every winter that face becomes a startline, 4x4s and buggies charging straight up it, engines screaming, most of them stalling and sliding back down. Out on the ridges a driver crests one, drops down its blind far side and climbs the next at an angle that feels wrong from where you are sitting. A camel does it at the speed people actually crossed this desert, moving between the oases and the coast. Camped down in a hollow between two ridges, you get the night sky in real depth, and on a still winter morning the same hollow can fill with fog, leaving the crests above it like islands. The dates are still the serious business. Every July the oases compete over rutab, picked soft and half-ripe, for prize money in the millions.