The Wheel allows the building of chariots, a fast offensive unit.
It is a prerequisite of engineering.
Civilopedia entry[]
One of the five great simple machines, the Wheel and axle greatly increased the load that a human or animal could pull by lowering the resistance to movement. The Wheel was also quickly turned into a weapon of war after its invention, especially in the adaptation of the Chariot. In addition to its use in transport, the Wheel became a vitally important tool in Engineering and in the Industrial Age. In the pre-Columbian New World, the Wheel only appeared in children's toys, partly because the mountainous terrain of South America made it less practical.