Complex sentence: Tradition states that the first building was constructed during the reign of Emperor Constantine I, only 100 years after the martyrdom of St. Lawrence, though the first written evidence is from 1300, when Pope Boniface VIII rebuilt the church and annexed an abbey to it.
Split into simpler sentences: Tradition states that the first edifice on the site was constructed during the reign of Emperor Constantine I, only 100 years after the martyrdom of St. Lawrence. The first written evidence of an ecclesiastical edifice on the site is from 1300, when Pope Boniface VIII rebuilt the church and annexed an abbey to it.