Types of climbing: By terrain: * Rock climbing is climbing on steep rocky terrain. * Mountaineering is climbing on mountains. * Ice climbing is climbing on frozen water features. * Mixed climbing is climbing on both frozen water features, as in ice climbing, as well as rocky terrain. * Bouldering is solo climbing on boulders and low rock walls. * Stack climbing is climbing sea stacks: near vertical columns of rock in the sea, near coasts. * Buildering (pun on bouldering) is climbing on the outside of buildings. * Indoor climbing is climbing on artificial climbing walls. * Artificial climbing tower is a wooden, plastic, or steel climbing wall used outdoors. * Recreational tree climbing is climbing on trees. * Professional tree climbing is climbing on trees for the purpose of hardware installation, pruning, or removal. * Rope climbing is the timed vertical ascent of a suspended rope using only the climber's hands.