again under Gregory XI. The return of the pope to Rome in that year unleashed the Western Schism (1377–1418), and for the next forty years, the city was affected by the divisions which rocked the Church. Early modern history In 1418, the Council of Constance settled the Western Schism, and a Roman pope, Martin V, was elected. This brought to Rome a century of internal peace, which marked the beginning of the Renaissance. The ruling popes until the first half of the 16th century, from Nicholas V, founder of the Vatican Library, to Pius II, humanist and literate, from Sixtus IV, a warrior pope, to Alexander VI, immoral and nepotist, from Julius II, soldier and patron, to Leo X, who gave his name to this period ("the century of Leo X"), all devoted their energy to the greatness and the beauty of the Eternal City and to the patronage of the arts. During those years, the centre of the Italian Renaissance moved to Rome from Florence. Majestic works, as the new Saint Peter's Basilica, the Sistine Chapel and Ponte Sisto (the first bridge to be built across the Tiber since antiquity, although on Roman foundations) were created. To accomplish that, the Popes engaged the best artists of the time, including Michelangelo, Perugino, Raphael, Ghirlandaio, Luca Signorelli, Botticelli, and Cosimo Rosselli. The period was also infamous for papal corruption, with many Popes fathering children, and engaging in nepotism and simony. The corruption of the Popes and the huge expenses for their building projects led, in part, to the Reformation and, in turn, the Counter-Reformation. Under extravagant and rich popes, Rome was transformed into a centre of art, poetry, music, literature, education and culture. Rome became able to compete with other major European cities of the time in terms of wealth, grandeur, the arts, learning and architecture. The Renaissance period changed the face of Rome dramatically, with works like the Pietà by Michelangelo and the frescoes of the Borgia Apartments. Rome reached the highest point of splendour under Pope Julius II (1503–1513) and his successors Leo X and Clement VII, both members of the Medici family. In this twenty-year period, Rome became one of the greatest centres of art in the world. The old St. Peter's Basilica built by Emperor Constantine the Great (which by then was in a dilapidated state) was demolished and a new one begun. The city hosted artists