Designed by Murphy/Jahn, Inc. architects, Cityspire is New York City's tallest mixed-use skyscraper. This glass tower of a primarily octagonal plan has short streamlined extension wings, the whole rising in triple setbacks, ending in a domed top at the height of 248 m (814 feet). The bottom 23 floors of the tower are for commercial use and above it are luxury apartments which increase in size the higher they are. The building was the 2nd tallest concrete skyscraper in the world when it was completed. A midblock pedestrian passage was completed on September 15, 1997, after 12 years since being approved by city officials, completing a network of public midblock walkways between West 51st and West 57th streets.