Travelling along the valley of the stream that connects Rosia to Montarrenti, the most antique and beautiful bridge of our territory appears on the left. Going over it, one reaches the ancient ruins of the monastery of S. Lucia and the Castle of Spannocchia. The bridge probably dates back to the thirteenth century, although some believed to identify elements of the Roman period. Here there was a road (whose pavement is still visible in some places) which connected the Merse Valley with the Maremma. There is a legend about this bridge; the beautiful Pia, unhappy wife of Nello Inghiramo de 'Pannocchieschi, passed on it to go into exile in Maremma, in the Castello di Pietra. This event was recalled by Dante Alighieri in the fifth Canto of the Purgatory:
“Deh, quando tu sarai tornato al mondo / e riposato de la lunga via, / seguitò ‘l terzo spirito al secondo, / ricorditi di me, che son la Pia; / Siena mi fe’, disfecemi Maremma: / salsi colui che ‘nnanellata pria / disposando m’avea con la sua gemma”.