You feel the river before you see it: a constant, metallic susurration that grows into a confident roar as the canyon narrows. At the Espiunca parking (Km 8), guides tighten helmets and hand out neoprene kits while the Paiva, a ribbon of green cutting through granite and schist, seems to dare the morning light. Within minutes you push off—cold spray on your face, the current picking up like a living engine. Rapids roll under the raft, then ease into glassy pools where kingfishers hunt and the cliffs let loose the scent of fern and wet stone.