Grosseto [ɡrosˈseːto] About this sound listen is a city and comune in the central Italian region of Tuscany, the capital of the Province of Grosseto. The city lies 14 kilometres (9 miles) from the Tyrrhenian Sea, in the Maremma, at the centre of an alluvial plain on the Ombrone river.It is the most populous city in Maremma, with 82,284 inhabitants.