707 17th Street, formerly known as the MCI Building and Arco Tower, and now known as the Jacobs Building is a skyscraper in Denver, Colorado. The building was completed in 1981, and rises 42 floors and 522 feet (159 m) in height. The building stands as the seventh-tallest building in Denver as of 2018. It also stood as the tallest building in the city at the time of its 1981 completion, and held that distinction for two years until it was surpassed by the 709-foot (216 m) 1801 California Street in 1983.