San Lorenzo was the parish church of the Medici family and they didn’t spare a penny on it!
The church contains bronze pulpits by Donatello and a staircase designed by Michelangelo. Also lovely little chapels and plenty of frescos!
Most interesting, though, are the Medici tombs. San Lorenzo is the burial place of all the major members of the Medici family. There is an extraordinary marbled cappella and the family is buried within or underneath this chapel. You have to pay an additional fee to gain entry to the cappella and see the tombs!
Michelangelo was commissioned to design several of the funerary works and they are considered to be some of his most important works.
Donatello is also buried in this church.
The facade of the church is actually still unfinished, just raw stonework, despite the fact that Michelangelo apparently submitted several designs for the facade.
Again, no pictures allowed, not even of the marble tombs (they are tough on this in Firenze!).