LOVE Milano! I would say a top 5 city in Europe.
seconded that the Duomo roof walk in a must, unlike many super touristy activities it's very worth it. incredible views. I think they're doing work on it still, so if you squint you can pretend you're climbing the roof of Sagrada Familia.
Navigli is the other side of touristy, it's pretty but I'd go there for a daytime walk rather than dinner or a night out. around here is also a lovely shopping area around the street Corso di Porta Ticinese with lots of architectural ruins, I'd really recommend. closer to the centre, a walk in the grounds of the castle and the adjoining park is very pretty if the sun is out.
Porta Romana is a really vibrant neighbourhood with loads of small wine bars spilling into the street. for a real Milanese pizzeria experience try Pizzeria COKE. the pizzas are literally too big for the tables, it's amazing.
nearby is the Fondazione Prada, which is 100% the MUST-SEE CULTURE SPOT of Milano. very chic space over about seven floors with exhibits by Koons etc and a cafe that resembles a real life Wes Anderson.
for a night out I would go to the Chinatown district and Via Paolo Sarpi. there's a wine shop called Cantine Isola that is four walls STACKED with wine bottles, you pick one for the night and they continuously fill your glass. everyone drinks on little stools in the street and gets Asian food nearby, it's so charming.
and finally for excellent Milanese pastries, try Marchesi 1824. there are three near Duomo, I think it's owned by Prada. remember NOT to order a latte or milky coffee after midday.
