A water irrigation system known as qanat emerged in the Iron Age (1,300-300 BC). This system provided a relatively constant water supply all year round by taking advantage of underground water supplies, leading to a change in settlement patterns as groups would follow the route of the water source.[13] Up until the mid 20th century (marking the beginning of Western attention to the area), most building fell into five categories: religious, residential, markets, public and defensive buildings. Buildings that were constructed up until then remained within traditional styles.