The Basilica of St. Peter in Chains is one of our "must visit" sites when we go on pilgrimage to Rome, and we have celebrated the Mass here several times. The basilica has been on this site from the 5th century, although it was renovated and rebuilt many times over the centuries.
It was built to house the relic of the chains with which St. Peter was bound when he was imprisoned in Jerusalem. The chains were a gift to Pope Leo I from the Empress Eudoxia. When he saw them, the Pope put them near the chains with with which St. Peter had been bound in the Mamertine Prison in Rome, and the story is that they were miraculously fused together. And there they are to this day, in a reliquary at the high altar of this basilica.
San Pietro in Vincoli is famous also for being the home of Michelangelo's magnificent statue of Moses. Sculpted in 1515 and intended originally to be one of forty statues comprising the tomb of Pope Julius II, the huge project was never finished. Instead, this single statue with its surrounding carvings serves as the memorial to the pontiff who was a major benefactor to the great artist.
The basilica underwent major renovations over the past several years, and on each visit we were able to follow the progress. On our last two visits we have been able to see it in all its splendor.