A sketch by Michelangelo for the dome of St Peter's Basilica has been discovered in the Vatican archives, the Vatican newspaper says.
The red chalk sketch, thought to be the artist's last before his death in 1564, provided a guide for stonecutters.
"The sureness in the stroke, the expert hand used to making decisions in front of unfinished stone leave little doubt, it is Michelangelo's," the paper said.
Michelangelo was named chief architect of the basilica in 1546, aged 72.
The chalk drawing is a "partial plan for one of the radial columns of the cupola drum of Saint Peter's," the newspaper L'Osservatore Romano said.
It is extremely rare, the newspaper said, because Michelangelo ordered the destruction of many of his designs later in life.
This particular sketch is thought to have survived because a building supervisor had used the back of it to make notes on problems linked to transporting the stone through Rome.