Founded by Cosimo the Elder, this library was extended by Lorenzo il Magnifico. The entrance is through an entrance on the left side in the church of San Lorenzo or through the delightful 15C cloisters (entrance to the left of the church). Its entrance resembles the exterior of a building. A monumental staircase designed by Michelangelo and built by Ammannati leads to a vast reading room, also by Michelangelo, where some of the 10 000 manuscripts are exhibited in rotation.