What to do in Milan?

Hi, since the people here were so helpful for my LATAM trip, I would like to use their kindness once again.

This time I have 7 hours in Milan, Italy.
Mind you - I have been to Milan before and saw the Milan Cathedral, the Grand Galleria, the Castello Forzesco, the Piaza del Duomo, and the Last Supper mural.

I would love to go see the opera but I wont be there in the evening.

So what should I do with my 7 (nett) hours during the day in Milan, in March. What would you do?

I am thinking about the Da Vinci museum of science and technology... anything else?

Ps- I like nature, animals and technology. And wouldnt be opposed to spending my day taking a class on something or some kind of workshop..

tips very welcome.

thank you.