You're not allowed inside the Duomo with your shoulders uncovered. We learned this the hard way. I was wearing a spaghetti strap dress (it's 92℉/33℃ and humid here in Milan), so they stopped my little group at the entrance, after we'd already purchased 3 tickets.

Luckily, we only had about 15 seconds of frustration. I said "Ah that's a shame", Sebastián responded "Oh I'm sure there's a shop around here somewhere", Tyler said "Markets in everything...", and then we looked up and sure enough there was a street seller approaching with an armful of 2€ kimonos!

We made it into the cathedral with barely skipping a step. Thank you, goddess of commerce.

The aftermath: