Ferrara is certainly one of the most livable cities in Italy, being the country's bicycle capital and having many green spaces. Its historic centre is quite interesting and pleasant, as well, but to me it did not appeal so much as a WH city. The cathedral and the Castello Estense, the city's landmark, are not bad (especially the moat), but nothing outstanding. I also saw the Palazzo dei Diamanti, famous for its unique wall, and the Palazzo Schifanoia, with its beautiful frescoes. To see the Po Delta part of the inscription, I took a bus out to Comacchio, a pleasant little town with a pretty Old Town and direct access to the canals and waterways that make up the delta. I just saw a small part of it, but I do believe that the Po Delta, as a unique cultural landscape, would easily stand on its own as a separate WH site, as I can't really see a very close connection to Ferrara (except for geographical reasons). Maybe then Ferrara should have been combined with Mantova as a pair of Renaissance towns.