Not anniversary time yet for us but for my birthday treat a fortnight ago we had a night in a hotel with an en suite bath so OH could have his first bath since October last year when we moved to our croft !
I am away, where I have access to a bath, for a fortnight in every six weeks, but I don't know how he has lasted so long! Hopefully we will have a bath installed in the house by this Christmas.
It was also the first night he hadn't slept on the croft since moving. We were only away for less than 20 hours but it was lovely and money very well spent.
So I would think along the lines of a similar treat again.