This ancient monolith rises 1.4 metres from the ground, its weathered surface telling a story that predates written history. The stone's distinctive shape; broad at the base where it measures 1.2 metres wide, tapering irregularly with the western edge narrowing to 66 centimetres and the eastern edge to just 42 centimetres; gives it an almost blade-like profile when viewed from certain angles. Oriented along an east-west axis, it occupies a commanding position on the northwestern edge of an area of high ground, where it has likely stood since the Bronze Age.

Standing stones like this one are amongst Ireland's most enigmatic prehistoric monuments. Whilst their exact purpose remains debated by archaeologists, they may have served as territorial markers, commemorative monuments, or held ritual significance for the communities that erected them. The considerable effort required to transport and raise such a massive stone suggests it held great importance for our ancestors. The Glenalla stone's prominent position on elevated ground would have made it visible from considerable distances, perhaps serving as a landmark for ancient travellers or a focal point for ceremonial gatherings.

This monument forms part of a rich archaeological landscape documented in the comprehensive Archaeological Survey of County Donegal, compiled by Brian Lacey and his team in 1983. The survey catalogued field antiquities spanning from the Mesolithic period through to the 17th century, revealing Donegal's deep historical roots. Today, the Glenalla standing stone continues to intrigue visitors and researchers alike, offering a tangible connection to Ireland's prehistoric past whilst maintaining its silent vigil over the changing countryside.