Good waste of OBC is to book a city stay with Celebrity
Book a private transportation to Rome maybe 100€, taxi to Rome to airport flat fee of 40€ $150 USD
a very good hotel 200€ a night or book a very nice Airbnb for 200€ a night , 400€ , $430 USD
you can find tours for $100 usd each day , so $400 for tour for 2
grand total $1000 ish USD
we spend 4 night pre cruise with our daughter and her husband , 2 bedroom Airbnb beside the Vatican Museum for $450 USD
I bet we didn’t spend $200 on tours for the 4 of us , transfer to port was $135 for 4
i find the researching trip the most fun