Excluding the outlying parks of Bois de Boulogne and Bois de Vincennes, Paris covers an oval measuring about  in area, enclosed by the  ring road, the Boulevard Périphérique. The city's last major annexation of outlying territories in 1860 not only gave it its modern form but also created the 20 clockwise-spiralling arrondissements (municipal boroughs). From the 1860 area of , the city limits were expanded marginally to  in the 1920s. In 1929, the Bois de Boulogne and Bois de Vincennes forest parks were officially annexed to the city, bringing its area to about . The metropolitan area of the city is .