Denver's finest example of French Gothic architecture is constructed of gray Bedford, Indiana, limestone over brick above a foundation of granite from Gunnison, Colorado. Matched spires with open bell towers, 210 feet high, flank a large rose window with stained glass angels playing classical instruments. A full-range carillon of fifteen bells occupies the east tower. Inside, the vault of the nave soars 90 feet. The highly detailed main altar, 30 feet high, is of Carrara marble, as are much of the statuary, the pulpit, and the bishop's chair. Leonardo da Vinci's The Last Supper inspired the altar table bas-relief, while Bartolomé Estéban Murillo's Immaculate

Conception was the model for the central statue above the altar. The exquisitely detailed stained glass was made by the F. X. Zetter Royal Bavarian Art Institute in Munich. The cathedral was elevated to a minor basilica in 1979 and underwent a $2.5 million restoration for the 1993 visit of Pope John Paul II. That project included a meditation garden with a wonderful bronze sculpture, The Assumption of Mary, which brings needed tranquility to worldly East Colfax Avenue.