Filippo Brunelleschi, the architect of the Duomo, went to Rome after he had lost a contest about the doors of the Baptistery of the Duomo. He lost in 1401 by Lorenzo Ghiberti for the design of bronze doors. Brunelleschi did not get the job. To recharge their batteries he went to Rome to study the buildings. Of course he was also at the Partheon. There he got the idea for his dome of the Duomo.
Piazza Del Duomo 1/7