Michelangelo was a multi-talented: artist, sculptor, painter, designer... His work also included architect & engineer for St. Peters Basilica at the Vatican. He spent considerable portions of his life at the Vatican and it bears his signature creations. Michelangelo is mentally and physically invested in the structures and images that define the spaces at the Vatican.
When Michelangelo was appointed as the key designer/ builder for the Basilica restoration, the dome was incomplete. He discovered why the project was delayed. The walls to support the dome planned were deflecting.
The solution Michelangelo devised was brilliant. It was so unique, he secured a "Interdiction" punishment from Pope Julius III - to prevent any subsequent design changes.
Michelangelo had a large chain made which he used to encircle the dome walls and enable the construction of the dome. He never lived to see it's completion.
The chains remains...
The Vatican page on Saint Peter's Dome is Here: