Medellín is the capital of Antioquia department and the second-largest city in Colombia. Officially designated the Special District of Science, Technology and Innovation of Medellín, it is situated in the Aburrá Valley within the central Andes Mountains in northwestern South America. The city proper had a population of 2,427,129 according to the 2018 census, while its metropolitan area encompasses more than 4 million people, making it the second-largest urban agglomeration in Colombia by both population and economic output.