Medellín , officially the Municipality of Medellín , is the second-largest city in Colombia and the capital of the department of Antioquia. It is located in the Aburrá Valley, a central region of the Andes Mountains in South America. According to the National Administrative Department of Statistics, the city has an estimated population of 2.44 million as of 2014. With its surrounding area that includes nine other cities, the metropolitan area of Medellín is the second-largest urban agglomeration in Colombia in terms of population and economy, with more than 3.5 million people.