Balancing the capitol and providing the necessary mass to complete a dominant east-west axis for Civic Center Park, this is the grandest monument of Mayor Speer's City Beautiful. Conceived as part of the original Robinson Plan of 1906, it took twenty-six years to materialize on its full-block site. The design was refined and implemented by a coalition of thirty-nine leading local architects. The Beaux-Arts Neoclassical facade has
three-story Corinthian entry columns of travertine atop a grand staircase. Unusual curving wings with engaged Doric columns reach toward the capitol or, some say, toward taxpaying citizens. Dressed Cotopaxi granite forms the base. Upper walls and the entry columns are Stone Mountain, Georgia, granite. Tremendous bronze doors in the pedimented entry portico open to an interior featuring eleven varieties of marble. Colorado travertine panels the main corridors and forms eight 19-foot-tall columns in the second-floor entry rotunda. It and the fourth-floor City Council Chambers are the most elaborate interior spaces.

The gold eagle and carillon clock tower capping this handsome city hall were donated in Mayor Speer's memory by his widow, Kate. The slender bell tower and the building's relatively low profile preserve vistas of the mountains from Capitol Hill.

Despite charges of bad taste and civil liberties suits, the City and County Building has been decorated riotously with colored lights every Christmas since 1932. A $10 million refurbishing in 1991–1992 brightened the interior and restored some features, including the grand lobby, Allen True's mural The Miners' Court, and Gladys Caldwell Fisher's life-size bas-relief Orpheus and the Animals. In the main entry lobby, 1993 works by Denver artist Susan Cooper depict Denver's architectural heritage.