What far fewer people realise is that the monument was built, at least in part, on top of something older: a military battery that once fired cannon salutes across the highest ground in the park, and which was quietly surrendered to make way for it.

The Salute Battery appears clearly on John Taylor's 1816 map of the environs of Dublin, positioned on the elevated ground that would shortly become the monument's footprint. By 1818, the fortification was described in Warburton and colleagues' survey of the city as mounting twelve pieces of cannon, twelve-pounders, fired on days of public rejoicing. The authors noted, with a certain dry realism, that such occasions were not likely to occur as often as formerly, and so the Board of Ordnance had already transferred the site to the Wellington Committee for the erection of what they called the Grand Trophy. By the time the Ordnance Survey produced its six-inch map in 1837, the battery was only partially visible as a hachured earthwork, the cartographic convention used to show raised or embanked ground, immediately to the east of the partially built monument. The battery had not been demolished so much as absorbed, its earthworks lingering beneath and beside a structure that was itself taking decades to complete.

Visitors to the Phoenix Park today will find the Wellington Monument accessible by foot from Chesterfield Avenue, the main road running through the park. The obelisk sits in an open expanse of grass, and there is nothing above ground to mark where the battery stood. The 1837 Ordnance Survey map, available to view through the OSi Historical Mapping viewer online, gives the clearest impression of what remained at that point, with the earthwork shown just to the east of the monument's base. Those with an interest in the palimpsest quality of the landscape, the way one use of land quietly overwrites another, will find something worth pausing over here, even if there is nothing obvious left to see.