One of the four major basilicas in Rome, St. Mary Major contains so much. In fact I know very little about it, so I’ll let these links speak for me:
https://www.basilicasantamariamaggiore.va/it.html
https://www.turismoroma.it/it/luoghi/basilica-di-santa-maria-maggiore
I did not attend mass here unfortunately, but I was sure to make the visit! Under the main altar rests the manger in which Jesus was born. Check it out:
Behind the main altar is one of the most stunning mosaics you will ever see:
JPD
Keep it up gorgeous.