Complex sentence: Since the 13th century, the lands of Bagnaia had been in the gift of the pope, usually given to the Bishop of nearby Viterbo, however, it was not until the 16th century that an episcopal residence was built there.
Split into simpler sentences: Since the 13th century, the lands of Bagnaia had been in the gift of the Pope, usually given to the Bishop of nearby Viterbo. However, it was not until the 16th century that an episcopal residence was built there.