The Edmund Rice Administration Wing, commonly known as The Castle, is a heritage listed building located on Mount Henry Road in Salter Point and the focal point of the Aquinas College Campus.

The building is owned by the Christian Brothers as part of the Aquinas College property.

The north wing, anticipated in the original plans, was designed by Henderson & Thompson and completed in 1967.

Deliberate efforts were made to design the north wing to echo the style, form and established materials of the original south wing, presenting visually, a three-storey façade, which cleverly conceal what is actually a four-storey building.

The Castle was funded largely by donations and from money obtained from the sale of some of the original 234 acres (0.95 km2) purchased by the Christian Brothers in 1928.