Matka Canyon hides a cave nobody has reached the bottom of. Divers have descended 212 metres into the flooded shafts of Vrelo and still found only more water below them, which puts it among the deepest underwater caves in Europe — and it lies barely 15 kilometres from Skopje. The Treska River cut this gorge through limestone, and in 1938 the country's first hydroelectric dam sealed off its lower end, drowning the canyon floor beneath a narrow green lake, the oldest artificial lake in North Macedonia. Ten known caves pierce the walls, and roughly a fifth of the canyon's thousand-odd plant species grow nowhere else on Earth. Among them is Ramonda nathaliae, a purple-flowered Ice Age relict that shrivels to a brown husk in the summer drought and comes back to life when the rain returns; it flowers on shaded rock from late April into May. Medieval monasteries stand above the water — St. Andrew's, founded around 1388 by a son of King Vukašin, and the Holy Mother of God — enough of them that Macedonians call the gorge a small Mount Athos.
Almost everyone starts at the jetty below the dam, where kayaks and small tour boats set off up the lake. The cliffs lean in until voices come back off the rock, and ten minutes upstream the boats tie up at Vrelo, where a lit walkway passes stalactites to two still cave lakes; the shafts the divers work drop away beneath them. The gorge is a protected monument of nature and the country's main climbing ground, its bolted limestone routes worked from Easter through November, while paths cut into the cliff face climb to the monasteries and the open ridge above. Come early: before the first boats the water lies mirror-flat, and by mid-morning in summer the coaches from the city fill the jetty.