The next step in agriculture after the plough is the organization of the collection and storage of the harvest timed by astronomy. Constructing a Granary increases the amount of food realized from the harvest and extends a city’s starvation protection to five turns. Even better, building the Stonehenge Wonder will give you a Granary in each of your cities.
People have been gazing at the night skies for as long as there have been people. Making star gazing useful, however, was a much later development. Once noticed, the fact that certain stars or combinations of stars appeared above the horizon at the same place and time each year was the basis for the transformation of star gazing into Astronomy, and its earliest use to time agricultural activity. The Sumerians and Babylonians had astronomically literate priests to chart the times for planting and harvest as early as 3000 BC, and the Egyptians were probably using astronomy to time the annual Nile floods even earlier. By accurately timing the planting and harvest of principle food crops, astronomy assured an annual supply and surplus of food, which in turn made city life possible. In pre-literate Briton, around 2200 - 1900 BC the Britons built the largest astronomical clock ever built: Stonehenge on Salisbury Plain. This enormous construction, originally in both wood and stone, is a good indication of how important astronomy’s calendar function was even to societies that were not concentrating their population into cities yet.