Once known as the Store House Tower or the Powder Tower, this circular mural tower, a tower built into or projecting from a defensive wall, occupied the north-eastern corner of the castle complex. It no longer stands above ground, but its base survives, and the story it tells runs considerably deeper than the medieval stonework itself.

Excavations carried out in 1985 and 1986 exposed most of the tower's base, which was found sitting directly on bedrock. The associated soil layers belonged to the fourteenth century and yielded pottery and coins, helping to date the construction and early use of the structure. What made the discovery particularly significant was what lay beneath and beside it. The tower had been built over a section of an earlier rampart, the defensive earthwork that had once enclosed the Viking town of Dublin. A stretch of medieval wall was also found abutting the Powder Tower, indicating that successive phases of fortification had accumulated on this corner of the site over several centuries. The work was documented by Lynch and Manning in 1987, with earlier reference by Healy in 1973.

The remains are not on public display in any conventional sense, having been uncovered during archaeological investigation rather than prepared as a visitor attraction. Dublin Castle itself is open to the public, and the State Apartments and the medieval Record Tower draw most of the attention. Those with a particular interest in the archaeology of the site may find it worth reading the excavation reports before visiting, as the physical evidence of the Powder Tower base is not signposted or immediately visible during a standard tour. The north-eastern area of the castle grounds is where the tower once stood, layered over a Viking-age boundary that quietly underpins the entire site.