When visiting Milan, you'll want to see the Milan Cathedral (Duomo di Milano). We decided to venture into the cathedral and even up to the rooftop terrace on this trip. To visit the Cathedral, you'll need to purchase tickets prior to getting in line for entry. If you haven't planned ahead, not to worry—you can still get them the day of. You can either purchase tickets in advance online before you go here or go to the ticket office in the morning. You can also go in for free if you're worshiping, but you won't be able to take photos.