I love this cathedral (duomo) and like the town a great deal too - Orvieto.
There is major art in one of the chapels inside, the chapel della Madonna San Brizio, with frescoes by Fra Angelico and Luca di Signorelli - well described in the book I'm reading again, Barbarian in the Garden by Zbigniew Herbert. Hard for me to recommend that book enough. He also tells a lot about how the facade came about over time. We only stayed there one day and night, nowhere near enough.
