Pune, formerly spelled Poona (1857–1978), is the second largest city in the Indian state of Maharashtra, after Mumbai. It is the ninth most populous city in the country with an estimated population of 3.13 million. Along with its industrial twin Pimpri-Chinchwad as well as the three cantonment towns of Pune, Khadki and Dehu Road, Pune forms the urban core of the eponymous Pune Metropolitan Region (PMR). According to the 2011 census, the urban area has a combined population of 5.05 million while the population of the metropolitan region is estimated at 7.27 million. Situated 560 metres above sea level on the Deccan plateau on the right bank of the Mutha river, Pune is also the administrative headquarters of its namesake district. In the 18th century, the city was the seat of the Peshwas, the prime ministers of the Maratha Empire and so was one of the most important political centres on the Indian subcontinent.