It was out of this deep, precipitous limestone quarry that stone for the ancient city was extracted. Riddled with catacombs and filled with citrus and magnolia trees, it's also where the 7000 survivors of the war between Syracuse and Athens in 413 BC were imprisoned. Its vaulted 'roof' of earth collapsed in the 1693 earthquake, leaving it exposed to sunlight and making it an ideal place in which to plant its current gardens.