Tianjin, alternatively romanized as Tientsin, is a municipality and a coastal metropolis in Northern China on the shore of the Bohai Sea. It is one of the nine national central cities in Mainland China, with a total population estimated at 15,621,200 in 2016. Its built-up area, made up of 12 central districts, was home to 12,491,300 inhabitants in 2016 and is also the world's 29th-largest agglomeration and 11th-most populous city proper.