We thought Ravenna was great with the Byzantine mosaics, but they pale in comparison to Monreale and Palermo. The Duomo is free and you can take photos (don't be the tourist who uses flash for a photo of mosaics 100 feet away). Relax and enjoy the environment. We were fortunate in that a wedding was also held at the same time and it was enjoyable to hear the organ music. Go late in the day to avoid the tour buses.
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