Jebel Shams is the highest mountain in Oman, but the reason to come is the hole in the ground beside it. Wadi Ghul falls almost a thousand metres in near-vertical limestone, the deepest canyon on the Arabian Peninsula and long nicknamed the Grand Canyon of Arabia. You stand on a bare plateau at the top of it with no railing anywhere, looking down at farms on the canyon floor that have shrunk to green specks. The mountain's name means Mountain of the Sun, because this is the first ground in Oman to catch the dawn. The true summit, just over 3,000 metres, is a closed military post, so travellers stop at the broad plateau a little lower, right on the lip of the drop. From there the canyon runs away below in bands of layered rock, and the opposite wall stands close enough to read every ledge and terrace on it.
Through the day the layered cliffs move through ochre, honey and ash-grey as the sun crosses them. In the last hour before sunset the light rakes the gorge side-on and the shadow line climbs the far wall. A narrow ledge known as the Balcony Walk traces the cliff face for a few kilometres to an abandoned hamlet, the drop falling away at your shoulder the whole way. The air up here stays cool while the lowlands bake, which is why Omani families drive up through the summer, and the unlit sky is among the best in the country for stars. Nothing is built on the rim: people pitch tents at the edge, cook outside, and wake to the sun striking the far wall first, exactly as the mountain's name promises. The nights are cold enough to need a jacket even in July.