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It’s possible to cover both Lucca and Pisa on a single day trip from Florence, as they are rather small towns. It is very convenient to move by train as the train stations of both Pisa and Lucca are located in the town center.
You can do Lucca in the morning, Pisa in the afternoon and then head back to Florence by the evening.
You can check train timetables on the official website of Italian Railways. There are fast trains (Frecciarossa) running from Florence to Pisa in about an hour.
In Pisa do concentrate your visit on the amazing Piazza dei Miracoli. The Best Day Trips from Florence is a post on the blog that can help you guide on what to visit having Florence as your base.
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