The Colorado capital is DENVER, which is a 6-letter word. DENVER is the most populous city in the state of Colorado and the capital of the U.S. state of Colorado. It is located in the South Platte River Valley on the western edge of the High Plains just east of the Front Range of the Rocky Mountains. DENVER is the 19th-most populous city in the United States, the fifth-most populous state capital, and the most populous city located in the Mountain states.