This is the Basilica of Saint Nicholas in Prison in Rome (Basilica S. Nicola in Carcere). It's on the Via Teatro Marcello, 46. Pilgrims from both East and West make pilgrimages to this church every year.
A friend asked me to "blog" the Roman celebration of the Feast of Saint Nicholas (a.k.a. Santa Claus) on December 6 and so I was there and these are the photos!
Although the body of St. Nicholas rests in Bari, Italy, there are two reliquaries in this church brought out every December 6 for the veneration of the faithful.