Matka is a limestone gorge fifteen kilometres from Skopje, in North Macedonia, and the green water on its floor was not there before 1938. That year the country's first dam closed the lower end and the canyon filled. The wall has had a second career since: it caught the crest of the Treska in the floods of 1962 and 1979 and held back water that would have gone straight into the capital. Kayaks and pedal boats go out from the jetty below it, and at water level the gorge closes around you, walls going straight up out of the green, side bays that the tour boats never turn into. If you stop paddling, the only sounds left are water dripping off the limestone and birds somewhere up in the cliff. Ten minutes upstream is the mouth of Vrelo Cave, where a lit walkway leads you past stalactites to two quiet lakes. They look modest; the deeper one is eighteen metres. The flooded shafts below them have taken divers 212 metres down without ever showing a floor.
The churches were here long before the water. The small church of the Holy Mother of God, at the canyon mouth, has stood since the fourteenth century and was repainted in 1497 by a noblewoman named Milica, its frescoes smoke-darkened and close enough to touch. A quieter path takes you up the far slope to St Nicholas Šiševski, with frescoes from the 1630s and an iconostasis of 1645, and enough churches in one gorge for Macedonians to call it a small Mount Athos. Climbers have five sectors of grey limestone rising straight off the lake, with belays on ledges above green water. The gorge has always been a hiding place. When the glaciers spread, it stayed sheltered enough for species that disappeared everywhere around it, and they never left; eighteen insects were first described for science here. The strangest survivor is the ramonda, which dries each summer into a curled brown husk and comes back with the rain. A botanist proved it by accident in 1928, wetting a specimen that had lain pressed in a drawer for eighteen months.