The ridge at the south-western edge of Galway's Townparks carries no plaque, no ruin, no trace in the ground of what once rose here: a massive fortification some six metres high and sixty metres square, with projecting angle-bastions at each corner, a surrounding fosse, and a gatehouse reached by drawbridge. St Augustine's Fort was, for roughly four decades in the early seventeenth century, one of the more formidable military structures in Connacht. Today, the only surviving evidence of its existence is the name of a graveyard next to where it stood.

The fort was built between 1601 and 1603, at a moment when control of Galway's harbour and the approaches to Loch an tSáile to the south carried considerable strategic weight. Its position on the summit of a steep-sided ridge gave clear sightlines over the town to the north-west and out across the water. What makes the site stranger still is what it displaced: an Augustinian friary had occupied the ground before it, and the church of that friary was not simply cleared away but actually incorporated into the fort's design. A place of religious community was absorbed, quite literally, into the geometry of military engineering, with its walls folded into an earth and stone construction of an entirely different purpose. Bastions, in the military architecture of this period, were the angled projections built at corners to eliminate blind spots and allow defenders to cover the walls on either side; the design here was square and regular, with one at each corner. Early seventeenth-century plans of the fort survive, along with written accounts discussed by Hardiman in 1846, and these give enough detail to reconstruct its scale and layout even though the structure itself was completely demolished in 1643, less than half a century after it was raised.