Complex sentence: Under this powerful family the city developed into a flourishing town, famous in the whole of Italy for its castle, which was enlarged, starting from 1470, by Napoleone Orsini and his son Virginio.
Split into simpler sentences: Under this powerful family the city developed into a flourishing town, famous in the whole Italy for its castle. The latter was enlarged, starting from 1470, by Napoleone Orsini and his son Virginio.