These three peoples lived in a vast area of modern-day Central and South America which incorporates coastal strips, hot and steamy jungles, savannah grassland and cold windy highlands. Though they spoke different languages, they had broadly similar cultures and they worshipped many of the same gods (although they gave them different names). They all used digging sticks, ate maize and beans, respected the number 13 and practised human sacrifice. Interestingly, although they developed the wheel as a toy, for some reason they didn't adapt it for other purposes. The Aztecs built their settlement in a swamp in what is now Mexico City and when the Spanish arrived they thought it more spectacular than Venice. The Aztecs were fantastic warriors but they were also excellent farmers: because they had stumbled on hydroponics, their floating fields produced an abundance of nutrients in the food they were growing. The Mayas built some of the tallest buildings of the ancient world � without the use of the wheel, or even horses. The pyramid El Castillo in Chichen Itza is the Mayan calendar, literally set in stone. Each staircase has 91 steps which, when added to the single step at the main entrance to the temple, totals 365 steps. At sunset on the spring equinox, the great serpents' heads at the foot of the main staircase are joined to their tails by a "body" of shadow. They developed a very accurate calendar that could predict solar and lunar eclipses, transits of Venus and - most importantly - the coming of the rains and the time to plant.