Blackrock Castle is a massive and ancient structure, built near the borders of the city centre and what is now known as Goblintown. Back during its originally construction, it used to look out onto the open swampland and plains, to Blackrock's east, and to the continent's interior.
None of the structure's original parts are thought to remain. Most recently it was rebuilt in a hexagonal shape, with massive towers at each of the corners. Nowadays the keep is in use by the City Watch, as offices, sleeping quarters and armoury, as well as the Watch's dungeons. While much of the rest of the structure is used by the Imperial Army. Namely the great hall, the workshops and chapel, which has been converted to a place of worship for the goddess Imperia.
The army also handles the duty of feeding their own, as well as the Watch and any prisoners kept at the castle.