Martvili Canyon is a limestone slot so narrow that in places only five metres separate the walls, with the emerald Abasha River running along the bottom of it. The colour is what people come for: the water drains off karst carrying fine mineral particles, so it holds a deep turquoise-green and goes glassy wherever the current slows. Waterfalls drop twelve to fifteen metres from the rim, Colchic forest closes overhead, and stone arches bridge the gap high above the water. The gorge runs 2.4 kilometres through the hills of Samegrelo in western Georgia. At one point thirty limestone steps drop to a pool at its foot, the bathing place of the Dadiani princes, who kept the best stretch of the river for themselves. The rock they cut those steps into is a Cretaceous sea floor, and it still holds ammonites, sea urchins and the footprints of plant-eating dinosaurs.
The canyon is visited in two parts, one on foot and one on the water. A 700-metre paved trail runs along the rim past the falls and down the Dadiani stair, and then you pull on a life jacket for the 300 metres the trail cannot reach. The walls lean in, the light turns green, the overhangs drip on your shoulders, and the raft is through it in about fifteen minutes. Martvili is a protected natural monument today, entry is ticketed, and swimming is not allowed — the pools are for looking at. Everything else depends on the river. After heavy rain and through the spring melt it runs high and cloudy and the rafts stay ashore; by late summer it drops, clears and turns its deepest green. Russia annexed the principality in 1867. Kutaisi is ninety minutes away, which is why most people meet this canyon on a day trip.