Caprona is between Pisa and Lucca and it has a little tower from where you can observe Caprona and around. This tower was mentioned in Dante Alighieri “The Divine Comedy” in Inferno XXI canto, where the poet describes the battle of August 16, 1289 between the Florentine Guelphs and Ghibellines of Pisa, which had participated in the attack on Vicopisano occasion, one of the most important strongholds ghibelline:
“così vid’io già temer li fanti
ch’uscivan patteggiati di Caprona
vegendo sé tra nemici cotanti“,
(Inferno, XXI, 94-96).
That it means “Thus issuing from Caprona, once I saw / Th’ infantry dreading, lest his covenant / The foe should break; so close he hemm’d them round.” (I took the translation in english here).