What makes the location quietly odd is its deliberate blindness in two directions: the mountains block any view to the east or west, yet on a clear day the tower could see another signal station on the Belmullet Peninsula to the north, about 12.6 kilometres away, and a third on the western tip of Clare Island to the south, roughly 22 kilometres distant. That narrow north-south corridor of visibility was precisely the point.

Built around 1806 by the British Board of Ordnance, the tower was one of more than eighty signal stations constructed along the Irish coastline in the first decade of the nineteenth century. The network formed a continuous chain from Dublin Bay, running clockwise around the entire coast to Malin Head in County Donegal, its purpose being to relay warnings of an approaching French invasion fleet using a naval signal post at each station. The threat receded and the system was abandoned by the mid-1810s. The Slievemore tower was originally two storeys, built of roughly coursed limestone rubble with squared corner stones, a slight outward lean to the base, and patches of lime render still visible on the east wall. Internally, the east wall held a fireplace flanked by alcoves on both the ground and first floors, with the distinctive shallow outward bowing of the wall indicating a chimney flue running through its thickness. Two square chutes pierce the east wall, one passing horizontally through to the semi-basement level, the other angling steeply upward into an alcove. The first-floor doorway opened onto the west wall, and bartizans, small corner turrets projecting from the face of a tower to allow defenders to look along the walls below, protected the north-east and south-east corners. Two early twentieth-century photographs survive: one shows the tower still nearly complete, with a narrow rectangular machicolation above the doorway; the second shows the upper sections of three walls already fallen.

The tower sits within a rectangular rubble-walled enclosure measuring roughly 54 metres east to west and 27 metres north to south, entered through a gap in the south wall. Within it are the foundations of what was likely a storage building at the north-west corner, and a small oval hut to the south that may have been built after the tower fell out of use. About 12 metres west of the tower, a partially infilled oval pit with coursed stonework still visible in places may be either the base socket for the signal mast or the remains of a lime kiln, a structure used to burn limestone and produce mortar or agricultural lime. The tower also sits in older company: a standing stone lies about 600 metres to the east, and an unclassified megalithic tomb roughly 1.65 kilometres to the west.