Palmyra is a caravan city in the Syrian desert whose colonnaded main street still runs more than a kilometre through the sand. It stands where it does for one reason: Efqa, a warm spring, the only permanent water on this stretch of steppe. Caravans crossing between Persia and the Mediterranean stopped at it, and Palmyra grew rich taxing them. In the 270s its queen, Zenobia, ruled as regent for her young son and pushed her armies across the Roman East as far as Egypt, until the emperor Aurelian besieged the city and took her back to Rome in chains. Caravan money built the Great Colonnade, 750 columns along a single street, of which more than 200 are still upright. The stone is honey-coloured and there is no shade anywhere, so the hour after dawn is when you walk it, the low sun raking gold down the whole length.
At the far end of that street stood the Temple of Bel, the largest religious building in the Roman Near East and in use for close to two thousand years, until ISIS dynamited it in 2015. You come now to cleared ground and a field of blocks, and it is the plainest measure of what was taken. The Monumental Arch, which marked the turn from the colonnade towards the public square, went the same year; what still stands tells you how high it reached and how densely every surface was carved. West of the city, dozens of tower tombs several storeys tall fill the Valley of the Tombs, where merchant families laid their dead for generations. On the ridge above, the thirteenth-century castle of Qalaat ibn Maan gives you the widest view over the ruins and the oasis. The water went too: Efqa ran dry in 1994, drained by drought and pumping after four thousand years. Khaled al-Asaad looked after Palmyra's antiquities for more than forty years and had moved hundreds of statues to safety before the town fell. ISIS held him and he would not say where. They killed him in August 2015, at eighty-two, and his killers never found them.