It's a widget storage depot. We have them all across the UK. When they first introduced widgets to the gromit industry, they had to be stored in a controlled environment to quite high standards in terms of the shape of warehouses. This particular design is known as the Red Brick Warehouse, on account of the materials used. The bricks are specially imported from the Spanish Main, as they are the right consistency to allow air in, to keep widgets cool, but not let the noxious vapours out. This is a fine example of an industry that no longer exists, and you're lucky your city has one.