Lucca is beautiful! I went there in October 2004 and it was still nice and warm. A popular choice is to rent bikes and cycle around the city walls for an hour or two. It is not expensive and there are loads of places renting bikes by the hour. I think 2 hours is a good amount of time to rent them for because you can also cycle around the town itself. they also have lots of good ice-cream parlours (to be expected in Italy!).