sentences:  A Roman smelting furnace was found at Colsterworth in 1931, as was a small defended Late Iron Age settlement in the 1940s.Colsterworth is raised upon a slight limestone ridge, with the River Witham running below on the western side and dividing the two villages.The old hamlet of Twyford has been incorporated by the growth of Colsterworth, but the name survives in the names of some houses and in Twyford Wood.