Tuscany is a region with a strong tradition of cycling; there are many interesting cycling routes, even if dedicated bike lanes are still quite rare; I refer here to only two climbs which I have tried personally, both interesting in terms of landscape and relatively peaceful: the climb up to S. Baronto (Pistoia) and that rather difficult climb to Tirli (Grosseto).
Another route, but on an unpaved bike path, is that of the Bandite di Scarlino.