The six-sided ring of Medici walls that circles the old centre of Grosseto is one of the best-preserved examples of 16th-century Renaissance fortifications in Italy. Commissioned by Cosimo I de' Medici in 1565, the walls replaced an earlier medieval circuit and were designed according to then-modern principles of artillery defence — six angular bastions giving overlapping fields of fire.
The entire circuit can be walked on the broad grass-topped ramparts in about 40 minutes. The interior of the walls has been converted into a public park with paths, benches, and shade — a genuinely pleasant place to walk in the evening. Two original Medici gates survive at the north (Porta Vecchia) and south (Porta Nuova) entries.