drive down to Trevi. This we did via Cortona / Perugia (outskirts only !) / Spello / Foligno (again, only outskirts) / Trevi. As we passed Assisi we said "No point going *there* -- not on a Sunday morning !"; and we didn't go any other time, because it was always completely shrouded in smog !
As we passed Spello we turned off for a quick peek and took a nice pic. in the morning sun; but although we then drove in for a bit of an explore, we found that *that*'s where all the people were, not in Assisi !, and NOWHERE TO PARK !!!
Amongst the *many* sites dedicated to castles in Toscana is this one, to castles in the Arezzo area
. It may interest you to check someone else's views of some of those we visited.