Gwalior is the fourth largest city of the Indian state of Madhya Pradesh where it serves as the capital and the administrative headquarters of the eponymous district and division. It is an important cultural, industrial, sports and political centre. Known as the music city of India, it is home to the oldest musical gharana of the Indian subcontinent and of the earliest known epigraphical inscription that uses the number 0 (zero) as part of the Hindu numeral system. The grand historic city and its fortress have been ruled by several Indian kingdoms from the Alchon Huns to the Gurjara Pratihara and Kachchhapaghata dynasties. Later it fell into the hands of the Delhi Sultanate before passing on to their vassals, the Tomars.