The results of archaeological excavations show that underground water supply system have been used  in Baku since 9th century. At that period, water wells provided  city’s water supply. In the XIV-XV centuries the water system was enhanced and improved gradually. According to the construction works a lot of  water wells were discovered. Water wells are conserved and maintained by the Icherisheher Administration. An interesting underground architectural building - a waterway was found around the  Maiden Tower, carefully drawn from pottery pipes. Currently, these water pipes belonging to the XII-XIII centuries are demonstrated at the Maiden Tower exposition.