Agra is a city on the banks of the river Yamuna in the northern state of Uttar Pradesh, India. It is 378 kilometres (235 mi) west of the state capital, Lucknow, 206 kilometres (128 mi) south of the national capital New Delhi and 125 kilometres (78 mi) north of Gwalior. With a population of 1,686,993 (2013 est.), it is one of the most populous cities in Uttar Pradesh and the 19th most populous in India. Agra can also refer to the administrative district that has its headquarters in Agra city. It is a major tourist destination because of its many splendid Mughal-era buildings, most notably the Tāj Mahal, Agra Fort and Fatehpūr Sikrī, all three of which are UNESCO World Heritage Sites.