You must go to the Vatican City if you are in Rome! If you want to beat the crowds though come early! We went around 9:00 a.m. and we had to wait around 20 minutes to get into the basilica. Within 30 minutes, we saw that the crowd wrapped around the main plaza area. Definitely worth it to come early. Also buy tickets beforehand for the museum and be prepared to be bombarded by people asking you to buy tickets.