Rome is really rich of sites and museums that have never been advertised.
Many famous sites are very chaotic and finding tickets is very difficult.
In the eternal city are many museum with incredible works of art and visit them is no different, probably can be better.
Ancient statues loved by the major artist such as Michelangelo, which were pure inspiration for them.
No problem to find tickets, no chaos, time to look at the works. and many different themes.
Enjoy Rome visiting museums not full of people.