Catacombs! Also, I remember some former Roman noble family house that was open to visitors, but alas, details have faded, except for the painted ceiling of gods, heroes, etc etc plus the rather pudgy head of said house in a toga, or what the Renaissance considered classical garb, anyway. Also, the Vatican: it's wicked rip-off expensive as I recall, and over the years popes have collected a lot of crap and kitsch as well as the Really, Outstandingly, Great Stuff, but the latter is worldclass ROGS, after all.