Milano will be at the seaside (like it was millennia ago), because there's water under this "Pianura Padana" plain (that's also why earthquakes are rare, there's also sand underground, brought by rivers from the mountains).
Milan will become capital city and with a population of more than 5 millions (as Milan anthem says: "...then everybody's coming to Milan")...well it is already, with the suburbs.
Venice (already a bit sunken city) and Rome will be flooded away (government included) and stop receiving money from the North, much to the Northern people amusement.
Finally, justice will be done.
The Holy See will become Holy Sea, lol.
If you noticed, there are already many disasters because of water (and stupid mayors).
Milan will save itself from the water because it's on a hill of 122 metres. And because Milanese people would be intelligent to move the whole city