The Cetina River drops 101 meters through a fifteen-kilometer canyon system between Zadvarje and Omiš, carving vertical limestone walls that rise 180 meters above the waterline. Geologists trace the gorge formation to tectonic uplift during the Miocene epoch, when the Dinaric Alps buckled and fractured, creating the fracture zones that channel today's river. The upper canyon remained inaccessible to wheeled vehicles until 1967, when Yugoslav engineers blasted a service road along the eastern rim; before that date, only shepherds and smugglers knew the trails. Whitewater rafting arrived in the mid-1990s, introduced by Croatian alpinists who had trained on Alpine rivers during the previous decade. The sport gained international recognition after the 2000 European Rafting Championships, held on a six-kilometer stretch below Blato na Cetini. The river's gradient—gentle by Alpine standards, averaging eight meters per kilometer—produces Class II and III rapids interspersed with calm pools, making it suitable for first-time rafters while still offering adrenaline spikes at Veliki Kuk and Mala Gubavica rapids. Seasonal flow varies dramatically: spring snowmelt from the Dinara massif pushes discharge above 40 cubic meters per second, while late-summer levels drop to twelve, exposing gravel bars and widening the navigable channels. Today's Cetina River rafting tour routes typically launch from Penšići, eight kilometers upstream of Omiš, and conclude at the town harbor where the river meets the Adriatic. Operators incorporate cliff diving from platforms ranging from three to eight meters, located at bends where the current has scoured deep basins. Several outfitters now include detours into karst caves accessible only by water—most notably a 40-meter tunnel beneath Velika Gubavica, where the ceiling drips with calcite formations and swallows nest in summer months. The canyon's microclimate supports Mediterranean and sub-Alpine vegetation within meters of each other: holm oak and Aleppo pine cling to sun-exposed south faces, while the shaded north walls host beech and hornbeam remnants from the last glacial period. Omiš itself, a former pirate stronghold, serves as the logistical hub; the town's medieval fortresses—Mirabella and Fortica—overlook the canyon mouth, offering post-rafting vantage points for those who climb the 300 stone steps to the upper ramparts.