Along the south wall of the gorge runs almost a kilometre of caves cut on six parallel levels and linked by tunnels: about 140 chambers, Sicel tombs that became houses in Byzantine times, known here as ddieri, from the Arabic diyar. The river Cassibile, the Kakyparis of the Greeks, shaped all of it, biting into the limestone to a depth of 507 metres below the belvedere at Avola antica, where the canyon also reaches its greatest width, 1,200 metres. The nature reserve dates from 13 July 1990, is run by the Sicilian regional forestry agency and covers 2,700 hectares, 900 of them fully protected and 1,860 as a buffer zone.
What to see
The valley floor is a chain of green pools joined by small waterfalls: locally they are called uruvi, and you reach them down the Scala Cruci, an old stairway cut into the rock. Around them grow huge oriental plane trees, dwarf palms and more than 400 plant species, among them Hyblaean endemics such as Trachelium lanceolatum and the rare Ophrys exaltata; in this damp, shaded bottom there are even snowdrops and a tropical fern, Pteris vittata. Peregrine falcons and buzzards work the air above; the freshwater crab Potamon fluviatile lives in the water, and porcupines, pine martens and the Sicilian pond turtle move among the rocks.
People have lived in the gorge for three thousand years. The Sicani cut a necropolis into places that are still almost unreachable; the northern rock village dates from the 11th and 10th centuries BC and lines up hundreds of chamber tombs and early Christian hypogea in six stacked rows. Also on the north side is the Grotta dei Briganti, some twenty rooms carved around a spring, reused by the Byzantines and then by the Arabs, who turned that water into a tannery. Just above the pools stand the ruins of a monastery and the houses of families from Canicattini who lived off olives, carobs and almonds until the last century. At the mouth of the Cassibile, in 413 BC, the Athenian general Demosthenes surrendered to Syracuse with 6,000 men; the painter Jean Houel came to draw the gorge in 1777.
Visiting
The rules of the managing body allow three routes only: the Scala Cruci and the Sentiero Carrubella, both reached from the SP 4 road between Avola and Manghisi, and the Scala Mastra Donna, from the SP 73 out of Canicattini. The descent is steep and has no water; the climb back is the part that really counts, and in summer it should be done early or late, never at midday. Landslides after heavy rain and fires, like the one on 25 June 2014 that burned much of the valley rim, close the paths for long stretches: phone the forestry agency first, on 0931 67450. Half a day at least, boots, water.
Our editors' tip
We start at first light from the belvedere at Avola antica: in raking light you can pick out the mouths of the ddieri on the far wall with the naked eye, and they are worth a look through binoculars before you go down, because from the bottom they disappear. Then down the Scala Cruci, a swim in the first pool before the sun clears the rim, and back up by ten. Bring a bag for your rubbish: nobody comes down here to collect it.