The City of Denver is the capital of the state of Colorado, and the County of Denver is the most populous municipality of that state. Denver is located in the South Platte River Valley on the western side of the High Plains of the Rocky Mountains. Denver is nicknamed the Mile High City because its elevation is exactly one mile above sea level, which makes it one of the highest large cities in the United States. With a 2013 population of 655,000, Denver ranks as the 20th most populated United States city. The Denver-Aurora-Lakewood area, comprising ten counties, had a 2014 population of over 2.5 million people, ranking it as the 22nd most populated metropolitan area in the United States. The Denver-Aurora area, composed of twelve counties, had a 2014 population of 3.25 million people, ranking it as the 15th most populated metropolitan area in the United States. The Denver Babes website lists additional escorts in Colorado.