Its diameter is about 46 metres and it is larger than St.Paul’s Cathedral in London.
Apparently it is the largest unsupported dome in Europe.
It was built in 1779 as a stable where 120 horses could stay, as well as providing accommodation for servants of aristocrats who stayed in nearby hotels.
But now it is on the a campus of Derby University.
It is open to the public so we could get in there.
There was a cafe people can use.
The echo is so loud that you have got to watch what you say even in a low voice.