The morphology of the current Valdelsan village of Castelnuovo and the surviving toponymy have made it possible to hypothesize about the nature of appearance the walled village must have had during the Late Middle Ages. The fiscal declarations of the mid-15th century inhabitants refer clearly to a "castle above" and a "lower village." Indeed, the current settlement is divided into two sectors that are distinctly different in terms of elevation: the upper part, corresponding to the current Piazza Indipendenza, and a lower part, clustered around the current Piazza della Repubblica. The "castle above" also had a free area, a small square, overlooked by the public residence of the officers of the small rural municipality. At the upper part of the castle, we still find today the rectory of Santa Maria, mentioned in a record in the Rationes Decimarum of the last quarter of the 13th century, which also functioned as the parish church for the castle. In the "lower village," concentrated around the road that connected the small castle with the other villages perched to the left of the Elsa (Varna, Catignano, Coiano), a reception structure operated, beginning from the 15th century, the hospital of Saints Lorenzo and Barbara. In that function, the structure replaced the older hospital, dedicated to San Iacopo, which before was on the same street, but on the opposite side, near the southern accesses to the Castle, where another small village outside the castle had already formed, Borgo Setta. The upper part of the castle and the lower village, the part most densely populated and closest to the main nucleus, were surrounded by walls, from which we can today see the material traces of two curtain towers. The defensive system of the small rural municipality, already compromised during the warring episodes of the second half of the 14th century, appeared to be in critical condition the following century. In 1436, in fact, an inhabitant of the castle registers a report on the damage to his house due to the collapse of one of the wall towers. However, at the beginning of the following century, Castelnuovo still had the appearance of a turreted castle, even though some structural alterations to the castle defenses were already in progress. This is the form in which it was seen and represented by Leonardo, even in the early 16th century. Of the walls and towers, probably in brick, there remain only a few traces visible along the roads of the current town. The rectory of Santa Maria Assunta, largely remodeled, preserves some portions of the original walls in its interior. On the portion not plastered on one of the internal perimeter walls we can see a portal with architrave and round arch and a small, splayed single-lancet window, both made of well-squared sandstone blocks. The body of the castle church was therefore made of stone, while the current bell tower, perhaps of a later period, was constructed entirely of bricks.