The original plan included two battlemented towers, but the north¬east one was not completed as Captain George Grey, Governor, curtailed expenditure on his arrival in 1841.
Security and prisoner observation, however, were not limited and Kingston’s semi-circular design incorporating the towers gave guards an uninterrupted view of the cells and exercise yards. As an added deterrent to escapees, outer walls were topped with loose bricks which even with the aid of a hook and rope would be difficult to scale.
The outer walls are built of limestone quarried from North Terrace near the site of the present Adelaide Railway Station, and the copings, sills, and towers are of sandstone imported from Tasmania. Building bricks came from brickyards in Hindmarsh.
The original two-storeyed cell blocks are protected by brick arcades, while the cells themselves have curved ceilings. One notable feature is the main gateway which is flanked by two Aboriginal heads, one a male and the other a female. Other heads, which are thought to be Gothic in design, adorn tower windows