I'd like to see and hear a range of very good large organs. I like the reverb that occurs in a large church or cathedral, so I would prefer that over a concert hall. Also, since I would like to hear it, I need a location which either has concerts or predictable times when you can hear practice. For example, once I was lucky enough to visit St Paul's Cathedral in London and happened to hear the organist rehearsing. There are also scheduled recitals, Sunday Organ Recitals, so that is one answer to my question.
Which are the locations of Europe's largest pipe organs and how can I find them?
I say Europe partly because I am in Europe, but also because I guess that the most impressive organs are here. I am happy to be proved wrong in this assumption.
You may ignore COVID-19. Assume that life eventually returns to normal and what used to be possible becomes possible again.
(The title and text is plural to indicate that I don't expect a single answer, but a range of recommendations of well regarded organs. I hope that this makes the question less opinion based.)
My interest is musical rather than religious, so I don't require any specific religion or denomination nor will I reject any. Ideally, I would like recitals unconnected to religious services, but that is not essential. I happy to behave appropriately and respectfully if I need to attend a service.
I am concentrating on cathedral or large church organs rather than the concert hall ones because the experience is quite different.