Take the chance of visiting the Medici Castle in Melegnano before going to the WWF Oasis of Montorfano, just outside town.

It will give you a wider scope of the natural environment while you pedal, if you are not tired, try to make a trip to Rocca Brivio, which often hosts classical music concerts on summer evenings. 
You will keep pedaling in the plains, among cultivated fields and farmhouses, passing by larger boroughs near the Lambro river from time to time.

Sant'Angelo Lodigiano makes for an ideal stop in the middle of the day; its basilica and castle (which hosts an interesting museum dedicated to bread) are certainly worth a vist.
The last stage of this itinerary is between the Lambro, the Adda and the Po and features several variations that will allow you to explore this zone by taking your time. Codogno is one of the most important towns in the area, a good starting point to go on along this series of itineraries. If you stay for a little longer in the Region, you could head to Piacenza with ease by crossing the bridge on the Po river.

From here, you can take other itineraries following the Po until its source, plus some that go northbound along the Adda river.