Built in the early 13th century at the behest of the Aldobrandeschi family, the Middle Gate gives access to via Talassese. The height of the gate was raised during the rule of the Republic of Siena (1331-1559), and the clock tower was built and incorporated into the new structure in 1850. The gate has a round archway which is surmounted by an ogival arch. Above the clock tower there is a spire with a sphere and an iron weather vane, which were added in 1851. It has three commemorative plaques: one of the plebiscite for annexation to the Kingdom of Sardinia (later known as the Kingdom of Italy) which was added in 1860, and two in memory of the victims of the bombing carried out by the allies during the Second World War.
