The signal tower on Great Blasket is not much to look at now; only small sections of its ground floor walls still stand, surrounded by a wide spread of collapsed stone. But the logic of its position is immediately legible. The slopes fall away steeply on either side, the Atlantic opens out in every direction, and the nearest stations in the same chain, one at Bray Head on Valentia Island about 24.5 kilometres to the south-south-east and another at Sybil Head roughly 10 kilometres to the north-north-east, would have been visible on a clear day.

The tower was built around 1804 to 1805 and completed, with its signal mast erected, by 1806. It formed one link in a coastal warning network of over eighty stations constructed by the British Board of Ordnance in the early nineteenth century, running clockwise from Dublin Bay all the way to Malin Head in County Donegal. The system relied on naval signal posts to pass messages rapidly along the chain; the idea was that an approaching French invasion fleet could be reported from the outermost islands inward before it reached the coast. The threat diminished after the mid-1810s and the whole network was abandoned. The two-storey square tower, roughly 5.85 metres on each side and built in roughly coursed rubble masonry, has been collapsing ever since.

Beyond the fallen walls, a sub-rectangular enclosure, approximately 50 metres east to west and 20 metres north to south, is still traceable as grassed-over banks and tumbled walling. To the west of the tower there is a more enigmatic feature: a neatly carved square stone block set in a circular hollow ringed by flat stones, with a central slot in which an upright stone now sits. This is likely the mount for the signal mast itself. Ordnance Survey maps from 1841 to 1842 show the enclosure with a slightly rounded western end; by the survey of 1914 to 1915 that rounded end had disappeared, suggesting the enclosure's present form is relatively modern. A further layer of history sits quietly nearby: a Second World War era marking, recorded as Eire Sign 38, lies just to the west of the station, a reminder that the island's ridge was still considered worth watching from above more than a century after the signal tower had gone silent.