Marsh Loop Trail, Concord, New Hampshire This 1.6-mile loop trail near Concord has an elevation gain of about 69 feet and is rated as easy. The multi-use trail can be used in both directions and has a moderate overall physical rating. Upon entering the woods, the Marsh Loop passes a wetland on the left with many snags, where you may spot birds or a beaver. Watch for great blue herons in a small pond near the trailhead. The trail is part of the broader Broken Ground Trails system and features connections to other loops in the area for longer hiking options.