Petra was carved, not built. Its temples, tombs and palaces were cut straight into rose-red sandstone cliffs, so the facades are the cliff — columns, pediments and doorways standing proud of rock that was never quarried or moved. The Nabataeans, desert traders, made this hidden valley their capital in the second century BC and grew rich taxing the incense and spice routes between Arabia and the Mediterranean. At its height perhaps twenty thousand people lived here, in a place that barely sees rain, on water the Nabataeans engineered out of flash floods. Then the trade moved to sea lanes, an earthquake in 363 AD wrecked much of the city, and Petra emptied. Local Bedouin never forgot it, but to the outside world it became a rumour until a Swiss traveller, Johann Ludwig Burckhardt, talked his way in disguised as a pilgrim in 1812.
The approach is half the drama. You enter through the Siq, a natural crack in the rock a few metres wide that winds for more than a kilometre with walls climbing as high as 180 metres. Then it parts, and the Treasury appears in the gap — a forty-metre facade, most likely a royal tomb, catching the light at the end of the shadow. Beyond it the valley opens into an open-air city: rows of carved tomb fronts, a Roman-era theatre cut into the hillside, and the huge Monastery, reached by roughly eight hundred rock-cut steps. Inside the chambers the sandstone runs in bands of red, purple and ochre, so the colour is raw geology rather than anything anyone painted. Barely a fifth of Petra has been dug out, and satellites were still finding new structures in 2016. It draws over a million people a year, and on Petra by Night candles line the whole Siq up to the Treasury.