Over the Mystic, the city’s first signed walking route, will be celebrated on Thursday during the city’s weekly Circle the Square activities. The 1.7-mile loop begins at the corner of High Street and Governors Avenue. Volunteers will give out maps and guides from 3 to 7 p.m. in front of the Medford Historical Society, 10 Governors Ave. Group walks will be held at 3:30 p.m., led by Mayor Michael J. McGlynn, and at 6 p.m. Walkers are asked to arrive 15 minutes before the starting time. The walks have been organized by Medford Mass in Motion, a group that promotes healthy living among city residents. For more information, visit Facebook.com/TeamMedford..