A team of scuba divers from Italy and Belgium have explored Matka's underwater caverns to a depth of 212m and still not found the bottom, making these caves among the deepest in Europe. Cave Vrelo is open to the public – you can enter the inky depths of the bat-inhabited cave by boat (a popular excursion) or hired kayak.
Boats depart from Canyon Matka Hotel. The trip takes about an hour. The same boat also runs transfers (one-way 30MKD) directly across from the kiosk to the start of a steep 20-minute uphill path to the medieval monastery of Sveti Nikola, but note that it's not possible to enter Monday to Friday. It takes about an hour of light rowing to reach the cave by kayak.