 Evidence of the presence of the Cualann Celtic people (an early tribe possibly noted on as the Cauci on Ptolemy's world map) can be found in various mounds and raths.Clondalkin is believed to have been founded by Saint Cronan Mochua as a monastic settlement on the River Camac over 1,400 years ago (possibly late 6th or early 7th centuries).The round tower was built perhaps two centuries later (circa 790 AD) as part of the monastery.