This is the £5m cannabis farm hidden close to Manchester's Piccadilly Station.
A former warehouse, it had been turned into what one witness described as "like a garden centre".
It took police two days to remove 4,000 plants from the 1960s building in Heyrod Street.
The sophisticated operation was discovered at about 5.30am on Monday when officers were alerted to several bags of drugs being found.
The plants covered four floors of the vast building which is also bordered by Adair Street and Betley Street.
One source said: "It was immaculate and laid out like a garden centre, with plants in precise rows just a few centimetres apart. There was a fridge, cooking facilities and sleeping materials.
There must have been tens of thousands of pounds worth of electrical equipment in there too to cultivate the crop."
Police confirmed the drugs seized were worth an estimated £5m.
Heyrod Street is in the middle of a warren of backstreets near the railway station and is dominated by the building which had been taken over by criminals.
Detective Inspector Geoffrey Machent, from GMP's Central District CID, said: "This is a substantial discovery which has been discovered by officers thanks to a member of the public .
"As a result of this find, we're removed a significant amount of suspected cannabis that may have ended up on the streets of Greater Manchester and is another step forward in helping to disrupt the production and distribution of drugs within our community.
"No arrests have been made but I would urge anyone with information about the find to come forward.
"The information we receive from members of the public is invaluable. Anyone with information about this find can call 101 quoting log number 394 of 12/04/2021, online at www.gmp.police.uk or to Crimestoppers anonymously on 0800 555 111.
"Anyone concerned or has any information about drugs in their area can call 101 or report it online."
