I did Milan in the summer 08. The Duomo is a must, you can see why it took 500 years to build. Do Not eat at a cafe/resturant within site of it, it cost me 190 euros for 5 salads and 5 cokes.
No ones mentioned Milan Castle, it’s about 10 minutes walk from the Duomo and has the park at the back of it. At the far end of the park is an Aquarium.
Don’t forget to sample the icecream, lots and lots of icecream.
The lakes are about an hour away, but well worth a visit.
We’re going back this summer, can’t wait.