This fragmentary round tower stands on the eastern slopes of Carrickgollogan hill, reduced to just the base or “butt” of what was once a complete medieval structure. Located southwest of the church at Rathmichael, only the lowest section survives to tell the story of this former ecclesiastical landmark.

The remaining foundation measures 5.4 meters in diameter with walls 1 meter thick, rising to just 1.5 meters above ground level. The construction uses coursed quartz and sandstone blocks, materials that reflect the local geology of the Dublin Mountains area. This combination of stone types demonstrates the medieval builders’ practical use of readily available materials from the surrounding landscape.

Despite its severely truncated state, the surviving base provides valuable archaeological evidence about the tower’s original scale and construction methods. The diameter of 5.4 meters indicates this was a substantial structure that would have originally risen to considerable height—typical round towers range from 20 to 35 meters tall, meaning the Rathmichael example has lost approximately 95% of its original height.

The careful coursing of the mixed stone materials shows that even at foundation level, the medieval builders employed skilled masonry techniques. The use of both quartz and sandstone suggests they selected stones for both structural integrity and workability, with the harder quartz providing durability and the sandstone offering easier shaping and fitting.

The tower’s position on the slopes of Carrickgollogan would have originally provided commanding views across the surrounding countryside and toward Dublin Bay. This strategic placement was typical of round tower sites, where the structures served not only as bell towers for monastic communities but also as highly visible landmarks that could be seen from great distances.

The complete loss of the upper structure; whether through deliberate demolition, gradual collapse, or stone robbing for other construction projects—represents the fate of many Irish round towers that survive today only as fragmentary remains or foundation courses.