The subsoil contains a large water table which is alimented by the Vardar river and functions as an underground river. Under the table lies an aquifer contained in marl. The water table is 4 to 12 m under the ground and 4 to 144 m deep. Several wells collect its waters but most of the drinking water used in Skopje comes from a karstic spring in Rašče, west of the city.