Around 200 plants were found growing in the old Nationwide building near the Man on the 'Oss statue in Queen Square yesterday.
The drugs farm was spread over three floors and the basement of the dilapidated former building society, where the electricity had been bypassed to power the drugs set-up.
Workers from Western Power had to dig up a section of the pavement outside the building to isolate the power supply on Thursday evening and an area next to the former building society entrance remained cordoned off on Friday afternoon, with two police vans parked nearby.
KFC had to close as a result on Thursday, although it and the Subway branch next door were open as normal on Friday morning.
Interactive map of the area:
Police officers, who were called at around 10.30am on Thursday, initially struggled to search all of the four-storey building due to its dilapidated state, with the challenge made even harder due to the large amount of pigeon droppings inside.
Nobody was found in the building, but specialists from West Midlands Police's Cannabis Disposal Team have since confirmed that around 200 plants were found at various stages of development, while there was also evidence of previous grows.
Photos taken by the cannabis team show the industrial nature of the farm, with rows of plants packed tightly together underneath grow lights and wires dangling down connecting the lamps to socket banks on the wall.
A large ducting pipe and fans had been installed for ventilation.
The electricity supply is believed to have been drawn from the basement although it is not yet known whose supply the power was taken from.
Nobody has been arrested.
A West Midlands Police spokesman said: "Police received a call at around 10.30am on Thursday that directed officers to the former Nationwide building in Queen Square, Wolverhampton city centre.
"Officers discovered an extensive cannabis farm set-up at the disused building, over three floors and the basement, with around 200 plants in various stages of development plus a significant hydroponics set-up.
"Western Power were called to make the property safe as the electricity had been bypassed and wiring was in a dangerous condition.
"No-one was present at the location and enquiries are underway."