Complex sentence: In 1516 Bishop Bonafacio Ferrero replaced the Romanesque façade with a Bramante-style portico, which in turn was changed to a Palladian style in 1854.
Split into simpler sentences: In 1516 Bishop Bonafacio Ferrero replaced the Romanesque façade with a Bramante-style portico. The Bramante-style portico was reworked into a Palladian style in 1854.