8. Cathedral of St. John the Divine
The Cathedral of St. John the Divine is the world’s largest cathedral, but remains unfinished. In cross-shaped churches, a tower or a dome is constructed over the intersection of the four arms of the cross; a junction called the “crossing.” Guastavino tiles were used to build the dome that hovers over St. John the Divine cathedral’s crossing, the side aisles of the nave, as well as the staircases.
The Guastavino tile system lends major stability to the dome, also making it one of the largest free-standing domes in the world. It is now near impossible that the cathedral will ever be completed, as new apartment buildings have risen where the trancepts would have been built.