The Marañón hot springs cave is at the base of a cliff. The cave is formed by erosion from heated spring water. The entrance is tight, about body width. The water in the cave is crystal clear and of an unknown depth. You can wade in at knee depth for a few feet and look into the abyss. If you’re feeling brave, it is possible to wedge yourself between the walls and let your legs dangle. As the heated water flows out of the cave it cascades back down to the Marañón. The water temperature of the spring is 100-103 degrees Fahrenheit.