The fortified center is well defined in its two parts: the fortress, or the original layout on the hill of Cerruglio, and the village below, also surrounded by walls. The fortress, on a triangular plan, is made up of a semi-cylindrical stone tower, located at the northern vertex of the layout, and two twin towers with a square base. The first one, which stands out for its excellent masonry in squared sandstone blocks, probably belongs to the most ancient fortification of Cerruglio, from the 13th century. The two towers with a square base and the connecting curtains belong, instead, to the new fortress, from the 14th century, in its later version, namely, that redone during the years of Emperor Charles IV (1369-1400). The area of the fortress, with its pre-existing elements, constitutes the center of convergence of the urban layout of the 14th-century village. The inhabited area, by contrast with what usually happens in newly founded medieval villages, did not develop upon a quadrangular layout, but rather came to be articulated on a pair of converging road axes, in the shape of a wedge. The streets are the current Via Roma and Via Carmignani, which converge near the fortress, in front of the collegiate church of Sant'Andrea, the village’s only open space. The accesses corresponding to the two road axes are Porta Fiorentina (to the southeast) and Porta Nuova (to the east). The village was equipped with three more gates: one, whose name does not remain, along the Pescia side; and two more to the north, Porta Lucchese and Porta Pesciatina. The current village blocks maintain the trace of the original layout created using rational subdivision of the space within the walls. The lots on which the buildings for dwellings were built then were small, about 5x12 meters, with the short side facing the road and development of the planimetry along the entire length, up to the side facing the secondary road at the back. The regular layout reflects the typical plan used in newly founded medieval villages. The walls, which surround the entire village, belong primarily to the 1333 construction works. They consist of series of brick arches covered with masonry of river pebbles and wedges, and can be seen along some parts of the village perimeter. The walls were interspersed with square-based towers, one of which remains in a well-preserved state, on Via Nuova, made entirely of bricks. One of the latest interventions took place around the middle of the 15th century, aimed at strengthening and prolonging the efficiency of the 14th-century fortress. The structure, in plastered brick, can be recognized by the presence of stone brackets and ogival brick arches with machicolations above a sandstone string course. Lastly, the Medici intervention, datable to the second half of the 16th century, on initiative of Cosimo I, primarily concerned the bastions for reinforcing the keep. The buttressed ravelin, the drawbridge, and the unfinished triangular bastions, positioned northeast and west of the fortress, are works dating from the 17th century.