A mural tower is a tower built into or projecting from a defensive wall, designed to give defenders a flanking line of sight along that wall, and this one is easy to miss precisely because so much of it has been swallowed by centuries of accumulating ground levels.

The tower dates to the early thirteenth century, placing its construction in the period when Dublin Castle itself was being established as a serious piece of Anglo-Norman military infrastructure. By 1585, records describe it as a small square tower of three storeys, suggesting it remained a functional, if modest, part of the castle complex well into the later medieval period. The Bermingham Tower, to which it is attached, takes its name from the Bermingham family and was one of the principal mural towers of the original castle. What is particularly striking about this smaller abutting tower is the discovery, documented by Clarke in 2002, that its lowest courses of masonry are now extant only below ground level, meaning the very foundations of a thirteenth-century structure are preserved beneath the present courtyard surface, invisible to anyone walking overhead.

Dublin Castle is open to visitors and guided tours are available, though access to the areas immediately around the Bermingham Tower is not always straightforward depending on events and ongoing works within the complex. The Bermingham Tower itself, at the south-western corner of the upper yard, is the landmark to orient yourself by. The small tower abutting its western side is not interpreted with signage in the way the more prominent features are, so it is worth looking closely at the fabric of the walls at that corner before moving on. The buried lower courses are not visible at ground level, but knowing they are there lends the whole corner of the castle a different quality, the sense that the medieval building continues downward into the ground, quietly intact beneath the surface.