Turin Cathedral is a Roman Catholic cathedral dedicated to Saint John the Baptist and seat of the Archbishops of Turin; built during 1491–98. The result was a church with precise geometric forms, a Latin cross basilica plan, an entirely round ceiling with two aisles separated from the nave by piers; an octagonal crossing tower rises above the junction of the nave and transept and a series of alternating hexagonal and semicircular chapels are created out of the side walls. The cathedral is clad with stone from the Bussoleno quarries, giving it the pale tone that distinguishes it so clearly from other buildings in Turin. The most important work on the cathedral, following its construction, was the chapel of the Holy Shroud, designed by Guarino Guarini to house and protect the holy relic, built in 1668.