Complex sentence: St. Clemens cathedral was heavily modified in the mid- 1400s in a hall church style; the choir and western section was rebuilt, a large tower, flanked by two chapels, was constructed at the western entrance and the church was made higher.
Split into simpler sentences: St. Clemens cathedral was heavily modified in the mid- 1400s in a hall church style. The choir and western section was rebuilt, a large tower, flanked by two chapels, was constructed at the western entrance and the church was made higher.