Old Iron Works, Mells (Fussells' Lower Works) (grid reference ST738488) is a 0.25 hectare biological Site of Special Scientific Interest, in the Wadbury Valley, south of the village of Mells in Somerset, notified in 1987. The site is a ruined iron works, which mainly produced agricultural edge-tools which were exported all over the world, and is now, in addition to its unique and major importance in relation to industrial archaeology, used as a breeding site by horseshoe bats. The block of buildings adjacent to the entrance is listed Grade II* and most of the rest of the site is a Scheduled Ancient Monument.