the Pantheon) to above sea level (the peak of Monte Mario). The Comune of Rome covers an overall area of about , including many green areas. Topography Throughout the history of Rome, the urban limits of the city were considered to be the area within the city's walls. Originally, these consisted of the Servian Wall, which was built twelve years after the Gaulish sack of the city in 390 BC. This contained most of the Esquiline and Caelian hills, as well as the whole of the other five. Rome outgrew the Servian Wall, but no more walls were constructed until almost 700 years later, when, in 270 AD, Emperor Aurelian began building the Aurelian Walls. These were almost long, and were still the walls the troops of the Kingdom of Italy had to breach to enter the city in 1870. The city's urban area is cut in two by its ring-road, the Grande Raccordo Anulare ("GRA"), finished in 1962, which circles the city centre at a distance of about . Although when the ring was completed most parts of the inhabited area lay inside it (one of the few exceptions was the former village of Ostia, which lies along the Tyrrhenian coast), in the meantime quarters have been built which extend up to beyond it. The comune covers an area roughly three times the total area within the Raccordo and is comparable in area to the entire metropolitan cities of Milan and Naples, and to an area six times the size of the territory of these cities. It also includes considerable areas of abandoned marshland which is suitable neither for agriculture nor for urban development. As a consequence, the density of the comune is not that high, its territory being divided between highly urbanised areas and areas designated as parks, nature reserves, and for agricultural use. Climate Rome has a Mediterranean climate (Köppen climate classification: Csa), with hot, dry summers and mild, humid winters. Its average annual temperature is above during the day and at night. In the coldest month, January, the average temperature is during the day and at night. In the warmest month, August, the average temperature is during the day and at night. December, January and February are the coldest months, with a daily mean temperature of approximately . Temperatures during these months generally vary between during the day and between at night, with colder or warmer