The Mrežnica carves a sixty-kilometer corridor through Karlovac County, but it is the fifteen-kilometer canyon section between Primišlje and Belavići that holds the river's densest sequence of travertine barriers. Over millennia, calcium carbonate deposits have hardened into natural dams, creating more than ninety waterfalls and cascades that range from knee-height ledges to four-metre drops. The result is a continuous staircase of turquoise pools separated by sculptured limestone lips, each polished smooth by centuries of flow. Unlike the region's underground karst systems, the Mrežnica canyon remains open to the sky, allowing sunlight to penetrate the water and illuminate the riverbed in shades of jade and cerulean. Mrežnica canyon kayaking emerged as a recreational route in the early 2000s, when local outfitters recognized the corridor's unique combination of accessibility and natural drama. The river's gradient is gentle enough for novice paddlers—no technical rapids, only short slides and pool-and-drop sequences—but the travertine formations demand active navigation. Paddlers slide over waterfalls, swim through plunge pools, and portage around taller barriers, turning each descent into a hybrid of paddling and canyoneering. The canyon's microclimate remains cool even in August, thanks to canopy cover from beech and hornbeam that line the upper banks. Water temperature holds steady at fourteen degrees Celsius year-round, fed by karst springs that surface upstream. The canyon's ecology is a product of its geology. Travertine forms only where water is saturated with dissolved calcium, a condition met by the Mrežnica's limestone catchment. As the river tumbles over each barrier, carbon dioxide escapes, forcing the calcium to precipitate and slowly build new rock. The process is ongoing: every waterfall grows incrementally taller, and moss-covered ledges harden into future cascades. This dynamic landscape attracted scientific attention in the 1980s, when geomorphologists mapped the canyon's travertine architecture and documented its role as a natural laboratory for sedimentary processes. Today, the canyon is protected under Croatia's Nature Protection Act, which limits motorized access and restricts dam construction upstream. For paddlers, the canyon offers a rare combination of wilderness immersion and logistical simplicity. Put-in points near Primišlje are reachable by paved road, and most tours conclude at Belavići, where shuttle vehicles wait. The river's clarity allows visibility to two metres, revealing trout and crayfish navigating the pools below. Kingfishers and grey wagtails are year-round residents, and otter tracks appear along gravel banks in the lower canyon. The experience is neither extreme nor passive—it asks for confidence in cold water and a willingness to commit to the descent, knowing that the only exit is downstream.