Peroxide and then hypochlorite bleach. Not at the same time. There are products that contain them if you can’t get them neat. In fact I recommend those.
Try the peroxide first. Dilute as necessary. Wipe or spray on. Leave it on for a while to loosen anything and everything it can. After a while fill with hot (60-80C) water, but beware of thermal shock. Leave to stand until warm, not hot. Try to clean the glasses as best you can. This may be all you need.
If not, try the bleach. Same steps, but make sure you’re in a well ventilated area. I’ve found that while it stinks up the place, the mould just peels right off and into the hot bleach solution.
If the glasses smell of bleach afterwards, fill with warm water and leave for a day or two. Repeat as necessary. The bleach will dissipate eventually.
Most of the old buildings (usually churches / cathedrals) here have been built upon and changed over the centuries so what you see above ground is still old, but it’s not - at least comparatively - ancient.
I’m in England. I may or may not be in a town that has something like that, but even the places that don’t have something are within a couple of hours’ drive of somewhere that does.
I will say that where I am is listed in the Domesday book, but that isn’t saying much to be fair.