It seems that this Magazyn in the slums area of the Klasztorna has gotten a lot of use through the years.
W grze Wiedźmin
The warehouse is where Vincent Meis conducts his little "sting operation" on the local Salamandra he's recently identified. When Geralt gets out of prison, the captain suggests that the witcher stay way from the warehouse in the slums, especially around midnight. A witcher's sword would not be needed then. Indeed!