It is gone now, with no surface remains visible, yet the documentary record left behind is precise enough to conjure the thing almost stone by stone: round on the outside, square within, two rooms on a timber loft, walls just under a metre thick and rising to about 6.7 metres, each room fitted with two loop windows for light and, presumably, defence. A mural tower, meaning a tower built into or projecting from a city wall rather than standing independently, this one passed through several hands and several names over the centuries, ending up on the 1863 Ordnance Survey map simply as 'Case's Tower (Site of)'.

The tower's earliest clear appearance in the records comes from 1471, when the Dublin Assembly Roll set out an agreement with one Robert Fitz Symon. The city granted him the tower for a term of one hundred years at a nominal rent of one penny per year, on condition that he rebuild it in stone and lime, battlements and all, roof it with oak timber covered in slates, and complete the work within two years. By 1585, when a detailed survey was carried out, the structure was still in the possession of his descendants, described as 'a smale round towre withowt, and sqware within' sitting roughly 44 metres east of Fyan's Castle and 53 metres west of Isolde's Tower, another mural tower on the same wall. By 1604 the tower is referred to in the Assembly Roll as 'Casses tower', after whoever occupied it at that time, and the name Casey's Tower also appears in later sources. By 1726 it was a ruin, with its southern side facing onto what was then called Blind Quay.

Essex Quay today runs along the south bank of the Liffey, roughly opposite the Four Courts. The spot where the tower stood was more or less opposite the former SS Michael and John's church, now a Viking and medieval heritage centre, which gives a reasonable sense of the location. Nothing is visible at street level, but the tower appears on John Speed's 1610 map of Dublin, accessible through Cambridge University Library's digital collections, marked just east of Fyan's Castle. The 1847 Ordnance Survey city sheet, available via UCD Library, offers another reference point. For anyone interested in the line of the medieval walls through this part of the city, the proximity of the recorded measurements between Fyan's Castle, Fitzsymon's Tower, and Isolde's Tower provides an unusually legible stretch of the old defensive circuit, even if none of it now breaks the surface.