Giotto's amazing Arena Chapel (Capella Scrovegni) in Padua, Italy Frescos of Giotto di Bondone in this chapel became a pilgrimage sport for later artists. (I would love to see it one day. Need to make a reservation months in advance.
Giotto: The Arena Chapel Padua Contains Fresco cycle completed in Focuses on the Virgin Mary and her role in human salvation. commissioned by Enrico Scrovegni to repent his sins of usury, his father features in Dante's poem about hell.