The former Brattle Square Church is the first building of H. H. Richardson's design to look recognizably Richardsonian, with round Romanesque arches at the entrance porch and in the tower. Although other architects had invoked the Gothic idiom in locally quarried Roxbury puddingstone, Richardson was the first to exploit the material's affinity for the Romanesque. Richardson created a T-shaped auditorium for the Brattle Square Congregational Church with a Sunday school and a campanile filling the re-entrant angles of the T. The soaring campanile, with its Bartholdi-modeled frieze depicting the sacraments, is particularly successful; the trumpeting angels at the corners earned the building its jocular sobriquet, “The Church of the Holy Bean-Blowers.” The costs of its construction having bankrupted the original congregation, the church has since 1884 been occupied by the First Baptist Society Church. They constructed balcony seating to correct terrible acoustics and filled the three rose windows with stained glass by L. C. Tiffany.