Santa Maria Maggiore is one of Rome’s basilicas. I still haven’t exactly figured out the difference between a basilica and a duomo (cathedral). The Archdiocese of New York has a cathedral (St. Patrick’s), while the Diocese of Brooklyn has a basilica (big hulking building in Sunset Park). Santa Maria Maggiore is built on the spot where the Blessed Virgin caused snow to fall in Rome; they re-enact this each year by scattering white flower petals. It is also the church where Palestrina was Kapellmeister (not sure what it is in Italian, so German will have to do).
There is also a statue of the Virgin doing what Tom calls "the big arms thing." You rarely see this in art; usually, only Jesus does "the big arms thing." In its treasury, there is a lovely presipio (crèche scene) carved out of stone.