A day in Pisa requires patience, as the city is crowded by visitors striving to see the main attraction – the leaning tower and the cathedral. Apparently many visitors only see the main attractions and skipping rest of the city. But I will suggest that you take time to see other parts of the city.
When you are at the Piazza dei Miracoli you can take a stroll on the new city wall – it’s inaugurated in 1156 – and have a good view of the Piazza with the crowd and a good part of the historic center.
If you come by car it is actually possible to find free parking, north of the Piazza dei Miracoli and only having to walk 1 km to the Piazza.