It has two cathedrals and is said to have more standing medieval churches - 32 - than any city north of the Alps.
But the 2011 Census has revealed Norwich had the highest proportion of respondents in England and Wales reporting "no religion".
The city's figure was 42.5% compared with a figure of 25.1% for England and Wales as a whole.
The question was the only voluntary one in the census and 7.2% of people chose not to answer it.
The census found the Christian population of England and Wales had fallen by four million to 33.2 million in the past decade.
In Norwich 56,268 people reported having no religion, but the census revealed a wide range of groupings within that category.
There were 169 Spiritualists, 131 atheists and 783 said they were Jedi Knights, a reference to the Star Wars films.
Sixty-five people gave their affiliation as Heavy Metal.
The Bishop of Norwich, the Right Reverend Graham James, was sceptical about the census' findings.
"Norwich is a city of churches. They are around every corner," he said.
"It's also a centre of vibrant Christianity today.
"The cathedral is seeing hundreds of worshippers every day during December and will welcome thousands on Christmas Eve and Christmas Day."
He said there were many other large and growing churches in Norwich of all denominations.
"So it seems doubtful that Norwich is a less religious place than anywhere else in the country," he said.
"It would not have above-average churchgoing rates if that was the case.
"But it may be a place where the vibrant presence of the churches means that people have to make up their minds about faith more definitely, and that's no bad thing."