St. Paul's Cathedral in London has a reverberation time of 11 seconds when empty:
https://www.sciencedirect.com/science/a ... 0X84905625
I heard a recital there in 1962 by the great (Sir) George Thalben-Ball. It was amazing - despite that very long reverberation everything was clear. I wish I'd kept a copy of the programme - he must have chosen it very carefully. In the final item he built up to full organ - or so we thought; but then he added Dome Tubas. I never knew an organ could sound so exciting!