St. Peter's Basilica
By the end of the 15th century (1400s), the old basilica was falling to pieces. Pope Nicholas V, (1447–55), was worried about it and got two architects, Leone Battista Alberti and Bernardo Rossellino, to make plans to restore it or build a new one. But Pope Nicholas had so many political problems that when he died, very little of the work had been done.