a polje is a large flat-floored enclosed depression formed in a karst area with surface stream and underground water discharging system or at the karst/non-karst contact zone (a marginal polje). a marginal polje receives water from the adjacent non-karst area, and forms a large depression on the karst side. this kind of negative karst landform is often cultivated or inhabited, particularly in areas of continuous fengcong karst. tongle yutang polje is an example, containing leye county town and several villages, such as tongle polje and liuwei polje in leye, fengcheng polje, poxin polje and dongni polje in fengshan.