We found this to be the number 1 tourist attraction. We booked tickets a few months in advance. We where glad we did so as it was sold out. The Last Supper is wonderful and we enjoyed viewing it. If you are not on a tour then you are just brought into the room to see it then after approx ten minutes you can exit through the gift shop. Not a lot to do in Milan in comparison to other Italian cities, so if you are going make sure you book this.