Enhanced descriptions from Syndetics:

From Glendalough in Wicklow to Kilmacduagh in Galway, and from Tory Island off the Donegal coast to Ardmore in Waterford, so-called round towers punctuate the Irish landscape in a memorable and often dramatic way. We know of the existence of over eighty examples, though it is likely that there were once many more, perhaps over a hundred in the country as a whole. While some have been restored, many survive as ruins, and a few are only known from historical sources. Most scholars believe that the Irish round tower must have been based on prototypes abroad, and there are depictions of round towers in ivories and manuscript illuminations, both European and Byzantine, from the sixth century onwards. But a century or more ago, the purpose of the towers was the focus of much speculation and eccentric theorising. For some they were fire temples, designed for sun worship; others saw them as primitive astronomical observatories. In Irish Round Towers Professor Roger Stalley looks into this and the other questions that surround these unique monuments to a lost time. Establishing the historical context of the towers, he asks: when were the towers built, who built them, and how were they built