Maine Highlands, Greenville, Maine Adventures Whitewater raft Penobscot River One of the many exciting things to do in this part of Maine is whitewater raft through the gushing water of the Penobscot River. This raft trip takes you through some of the pristine wilderness that the Maine Highlands is known for. When running a river, it is important to go with professional guides like those of the New England Outdoor Center.