The population of the city of Bidar is more than 2,00,000, and the most widely spoken language of the region is Kannada. The city serves as the headquarters of Bidar district and is located on a hill top in the centre of the Deccan Plateau at an elevation of about 2,300 feet. According to the 2011 census, the population of the district is 1.7 million out of which 41 percent are in the working age group. 60 percent are engaged in the agricultural sector, 2 percent in the household industry and 38 percent contribute to the services sector and industry. Excavations carried out by the Archaeological Survey of India in this region have revealed several monuments, largely tombs, in and around the city, giving Bidar the name of The City of Whispering Monuments. The Bidar Fort was constructed between 1426 and 1432 by huge blocks of Black Stone, at a time when the capital of the Bahamani Dynasty shifted here from Gulburga. The Bahamani Sultanates also introduced the craft of Bidriware. Historically, this region was a part of the great empires of the Mauryas, Satavahanas, Kadambas, Chalukyas and Rashtrakutas. The Ancient Karez or Qanat System, which is an underground network of aqueducts for water supply has recently been discovered in the city of Bidar. The Bidar Karez, built in the 15th century, is more than 3 km long with 21 air vents and was necessary in a city where the soil was rocky and drilling wells was difficult.