 If a castle was under attack, a fire would be built on top of the castle, which could be seen for about fifty miles around, or to the next tower castle.The ruins of these castles, spaced about fifty miles apart can thus be seen periodically as one travels throughout the country.David Sweetman wrote "The great age of Irish castle-building began with the arrival of the Anglo-Normans, traditionally dated to 1169, and continued right up to the seventeenth century."