The inside of the cathedral of Pisa is as beautiful as its exteriors. If you paid to climb the tower, your ticket is valid for the cathedral as well.
Pisa is of course not just the Leaning Tower. There’s more to this charming city if you care to take a leisurely stroll back to the main bridge, the Ponte di Mezzo, that crosses the Arno river (yes, the same river that cuts through Florence).
Grab a map and explore. The city is compact enough to not worry too much if you get lost. Remember to stop for a few scoops of gelato.