"The famous St. Basil's Cathedral was commissioned by Ivan the Terrible and built on the edge of Red Square between 1555 and 1561. Legend has it that on completion of the church the Tsar ordered the architect, Postnik Yakovlev, to be blinded to prevent him from ever creating anything to rival its beauty again. (He did in fact go on to build another cathedral in Vladimir despite his ocular impediment!) The cathedral was built to commemorate Ivan the Terrible's successful military campaign against the Tartar Mongols in 1552 in the besieged city of Kazan. Victory came on the feast day of the Intercession of the Virgin, so the Tsar chose to name his new church the Cathedral of the Intercession of the Virgin on the Moat, after the moat that ran beside the Kremlin. The church was given the nickname "St. Basil's" after the "holy fool" Basil the Blessed (1468-1552), who was hugely popular at that time with the Muscovites masses and even with Ivan the Terrible himself."

Quote from http://www.moscow-taxi.com/sightseeing/red-square/st-basils-cathedral.html