Pork Futures Warehouse
The Pork Futures Warehouse is a product of the Disc's general atmosphere of magic and Ankh-Morpork's general atmosphere of excessive literalism. The trading in pork futures – pork which does not exist yet – led to the construction of a warehouse in which to store it until it does. Pig carcasses can be seen hanging from its ceiling, semitransparent and unreal.
Something in the unreality or odd time flow of the place produces very low temperatures, making it a very good place for trolls to be smart in – always providing they can get out again – as it is apparently cold enough to freeze even a living rock to death (see Men at Arms, Thud!).