Among the most dramatic and enigmatic of archaeological features gracing the Irish landscape is the round tower, the origins of which have had their share of controversy. Dating from about the early 10th to early 13th centuries, there are now about 60 remaining - "some have been restored, many survive as ruins". There were others however, such as that which once stood at the famous monastic site of Clonard, Co Meath. According to the annals for the year 1039, that tower simply "fell down to the earth". Another failing to survive the test of time, or more accurately, its inherent structural weakness was that at Ardbraccan, Co Meath, which collapsed in 1181. Whether intended as defence or sanctuary in time of invasion, or as a celebration of God, as bell towers calling the monks to prayer, or as a more earthy gesture towards man himself, the towers at their finest, such as at Ardmore Co Waterford or Rattoo, Co Kerry, are remarkable feats of engineering. (In 1832 one Henry O'Brien, who had a theory they were relics of phallus worship, was awarded £20 by the Royal Irish Academy for his research, or possibly, as Stalley argues, "to keep him quiet".) The antiquarian George Petrie was an early, if cautious, pioneer in Round Tower scholarship. Continuing the invariably useful, at times outstanding Irish Treasure Series, this brief introductory guide offers a concise, informative and engagingly anecdotal text with a generous range of illustrations. Stalley is Professor of History of Art at Trinity College, Dublin, and also wrote an Irish High Crosses guide published earlier in the series.