The Cetina River carved its 105-kilometre gorge through Dinaric limestone over two million years, leaving vertical drops that reach 180 metres in places and creating the technical playground now synonymous with extreme canyoning Cetina River expeditions. The river's canyon section near Zadvarje, 15 kilometres upstream from the Adriatic coast, compresses into a narrow corridor where water temperature holds at 8–12 degrees Celsius year-round, fed by karst springs that emerge from subterranean aquifers beneath the Dalmatian hinterland plateau. Croatian mountaineers first descended these walls with static rope in the early 1990s, but commercial canyoning operations only established themselves after 2005, when Zadvarje's limestone cliffs became accessible through bolted anchor systems that meet UIAA vertical safety standards. The Cetina gorge functions as a natural choke point where the river's flow accelerates through sculpted chutes and plunge pools, some exceeding eight metres in depth. The canyon's microclimate remains 6–10 degrees cooler than the coast, a thermal gradient that draws Split and Omiš visitors inland during July and August. Geologically, the gorge exposes Cretaceous-era limestone beds tilted at 40-degree angles, their stratification visible in the canyon walls where iron oxide staining marks ancient water levels. Endemic Balkan trout still inhabit the upper pools, though commercial descents concentrate on the middle section between the Gubavica waterfall and the Zadvarje bridge, a 1.2-kilometre stretch that includes four major rappel stations and twelve technical obstacles. Extreme canyoning Cetina River tours target the 50-metre Velika Gubavica waterfall, the canyon's most sustained vertical descent and the only rappel in the Dalmatian region that requires double-rope technique for safe passage. The waterfall's curtain flow increases eightfold during spring snowmelt, but summer levels stabilize at 2–4 cubic metres per second, allowing guides to position rappel lines through the cascade's edge rather than its direct impact zone. The canyon's lower exit at Radmanove Mlinice, a 19th-century mill complex now converted to trout farm infrastructure, marks the end of the technical section where the gorge widens and the river's gradient eases to less than two percent. Most commercial operations maintain a 1:6 guide ratio and require participants to demonstrate comfort with water immersion and vertical exposure before committing to the descent, a policy formalized after Croatian mountain rescue protocols were updated in 2019.