On an island with steep rock faces, mountain climbing is -- not surprisingly -- a popular outdoor activity. The Acadia Mountain Guides Climbing School (198 Main St. 207/288-8186 or 888/232-9559. www.acadiamountainguides.com) has private and group instruction for rock and ice climbing. In summer the school sponsors weeklong camps for teens. The Atlantic Climbing School (24 Cottage St. 207/288-2521. www.acadiaclimbing.com) offers instruction for climbers of all skill levels. It can tailor its climbs for families or groups.