Chennai is the capital of the Indian state of Tamil Nadu. Located on the Coromandel Coast off the Bay of Bengal, it is one of the biggest cultural, economic and educational centres in South India. According to the 2011 Indian census, it is the fifth-largest city and fourth-most populous urban agglomeration in India. The city together with the adjoining regions constitute the Chennai Metropolitan Area, which is the 36th-largest urban area by population in the world. Chennai is among the most visited Indian cities by foreign tourists. It was ranked 43rd most visited city in the world for year 2015. The Quality of Living Survey rated Chennai as the safest city in India. Chennai attracts 45 percent of health tourists visiting India, and 30 to 40 percent of domestic health tourists. As such, it is termed "India's health capital". As a growing metropolitan city in a developing country, Chennai confronts substantial pollution and other logistical and socio-economic problems.Chennai had the third-largest expatriate population in India at 35,000 in 2009, 82,790 in 2011 and estimated at over 100,000 by 2016. Tourism guide publisher Lonely Planet named Chennai as one of the top ten cities in the world to visit in 2015. Chennai is ranked as a beta-level city in the Global Cities Index and was ranked the best city in India by India Today in the 2014 annual Indian city survey. In 2015 Chennai was named the "hottest" city (worth visiting, and worth living in for long term) by the BBC, citing the mixture of both modern and traditional values. National Geographic ranked Chennai's food as second best in the world; it was the only Indian city to feature in the list. Chennai was also named the ninth-best cosmopolitan city in the world by Lonely Planet.