A promontory fort is exactly what the name suggests: a headland or coastal spur where the sea does much of the defensive work on two or more sides, leaving only a narrow neck of land for the builders to seal off with a bank, a ditch, or a stone rampart. The result is a fortified enclosure that is at once dramatically exposed and remarkably hard to approach.

These structures are generally associated with the Iron Age, though some were built or reused well into the early medieval period. Along the western seaboard of Ireland they are relatively common, a reflection of how seriously coastal communities took both the threat of seaborne attack and the strategic value of high ground with long sightlines. The Galway coastline, with its indented bays and jutting headlands, offered no shortage of suitable positions. Eochaill, whose name in Irish suggests a place of yew trees, sits within a landscape that has been farmed and fished for millennia, and the fort here is one of several markers of that long occupation.