Right you are, Borisborough: the Italian State Museums are free on the first Sundays of a month. That's also the WORST time to try and see the most-visited of them as the queues can be endless, at least during high and shoulder seasons. That the Vatican Museums in Rome are closed on Sundays (with the exception of shortened hours on last Sundays of the month when they're free) doesn't help. The exception is Galleria Borghese which mandates an advance (free) timed-entry reservation on first Sundays to keep the crowd size under control.
Although free, tickets also now mandatory for first Sundays at the Colosseum but cannot be ordered in advance.They're obtained on a first come, first served basis at on-site ticket offices: That's where those long queues will be.
https://colosseo.it/en/faq-tickets/
Queues are/were probably at their shortest in January. I've no idea if the same will be true during a Jubilee Year. The last one wasn't as heavily attended at expected but the city has poured a lot of $$$ into renovations and cleanings of monuments and improvement of some transport systems for this one so....
[ Edit: Edited on 19 Dec 2024, 11:34 GMT by goodfish ]