Well, we weren't sure if we wanted to climb the bell tower. We knew the views would be good, but... it's a long way up. We were surprised that it wasn't so exhausting, since there are multiple levels to stop at. I thought I'd be dead after we were back down to the bottom, but taking your time and looking around at each level broke it up. Bring your map and puzzle out all the different bell towers and landmarks. You also get a great look at the Duomo itself. The construction of the tower is interesting enough, too. I wouldn't say it's a must, because it's very time consuming, but I recommend it if the day isn't too hot and crowded. It would be tough on the narrow stairs during busy times.
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