The guns themselves are long gone, but the traversing platforms, the ruined guardhouse behind them, and the general logic of the compound remain legible. What looks at first like a modest ruin was once one node in an interlocking chain of coastal artillery designed to make Killiney Bay impassable to an invading fleet.

Construction of the Dublin-area Martello towers and their associated batteries began in 1804, directed by Colonel Benjamin Fisher of the Royal Engineers, and by December 1805 every tower along the coast had been armed and declared complete. Battery No. 9, as it is designated in the record, contained three gun emplacements oriented to cover the sound to the north, east, and south. The compound also housed a shot furnace, used to heat cannonballs to red heat before firing them at enemy ships, a standard feature of coastal batteries of the period, and quarters for a garrison of twelve soldiers. The battery and its adjacent Martello tower, a thick-walled cylindrical fortification of a type developed in response to Napoleonic expansion, were together armed with five 24-pounder guns. The Martello tower stands about 155 metres to the north-west, within musketry range of the battery, a deliberate arrangement that allowed the two positions to support each other. The concern prompting all of this had been articulated a decade earlier: in 1795, Lord Carhampton had identified Killiney Bay as a dangerously convenient landing point for a hostile force. The overlapping fields of fire from the batteries along the shore, reaching as far south as Bray, meant that at low tide the full extent of the beach could be covered by canister or grapeshot.

Dalkey Island is accessible by short boat trips from Coliemore Harbour in Dalkey village, with seasonal services typically running in summer months. The island is otherwise uninhabited and has no facilities. The battery sits at the island's southern end; the Martello tower is visible to the north-west as you approach the ruins. The iron rails and pivot fittings described by historian Paul Kerrigan in 1995 remain among the more specific things to look for, giving a concrete sense of how the guns were mounted and swung to track a target across the water.