Our guide -Alessandro-was friendly and knowledgeable. Started at Last Supper and he provided a great description if the fresco and its history. Tour of Milan and outside of castle was also great (info you just wont get on a self guided visit). The walk to the Duomo (via the galleria) provided a lot of history. The tour of the Duomo was great as he pointed out the significant artwork and unique features (like which part of the floor was old). A great guide makes a huge difference.