Waterline Trail Loop is a 5.4 mile loop trail located near Helena, Montana. The trail is primarily used for mountain biking. 5.4 miles 650 feet Loop mountain biking Expand Map VIEW FULL MAP Sign up now to see this map! Reviews (1)Photos (4)Recordings (0)Abby Northruptrail running1 year agoA nice and flat trail, some rolling. Very pretty and popular for the locals.