Actually there are so many things to see in the Knights’ Square ( in Italian: Piazza dei Cavalieri),
as the Palace of the clock.
This palace was built by Giorgio Vasari in 1607 on two old buildings incorporating the remains of the Tower, known as the Hunger one (della Fame): in this tower, so the story goes, the count Ugolino della Gherardesca, commander of the Pisa fleet, was condemned, after a defeat attributed to his treason, to die of hunger... with his children, treachery being, as is well known, a hereditary trait.
Hence the name of palazzo della Gherardesca that is sometimes given to the palace.

In "The Inferno", Dante and Virgil witness the soul of Count Ungolino, frozen within the ice of Cocytus' second round, Antenora.
He is gnawing on the head of his lifelong foe, Archbishop Ruggieri, and he tells Dante and Virgil his sad story on how Archbishop Ruggieri turning on him resulted in Count Ugolino's ultimate imprisonment and death from starvation.