The Southborough Open Land Foundation is commemorating its 25th year on Sept. 15 with a day of fun at Beals Preserve, on Main Street across from Chestnut Hill Road. From 1 to 5 p.m. there will be music by the Blackstone Valley Bluegrass Band, nature-related children’s activities, walks led by naturalists, a silent auction, and art displays along the trails. The event is free and will be held rain or shine. The organization was founded in 1988 to preserve, protect, and enhance the natural resources in town. Since its creation, the foundation has preserved 17 properties totaling 181 acres of open space. Visit www.solf.org for more information.