"Cappella degli Scrovegni" by Giotto, 1304-06, Padova, Italia. (Padua, Italy). This place is stupendous. It's worth a trip to Padova, (which is 20 minutes by train from Venice, and a beautiful city) just to see it. Warning: you need reservations. I lucked out the 1st time; couldn't get in on my 2nd trip.