Is also in the piazza del duomo, which is open march to october 9:00-1:00 & 3:00-7:00, november to february 9:00-1:00 & 2:00-6:00. they offer free maps, a room-booking service, bus tickets, a free bag check, & €5, 2 hour audioguides for exteriors only. this is also where a walking tour starts from at 3:00 daily except sunday, in english & italian, march-october, for €15
If you want to escape the crowds of tourists, there is a footpath that runs around the outside of town that is peaceful and affords some nice views of the countryside. It doesn't seem to go all the way around town, but it's long enough to work up a good thirst. Look for the signs with an icon of a hiker.