Castlecomer is on the gentle River Dinin, some 18km north of Kilkenny city. The town became a centre for anthracite mining after coal was discovered nearby in 1636; the mines closed for good in the mid-1960s. Anthracite, a very hard form of coal, burns cleanly and produces almost no smoke.
About 10km southwest of Castlecomer is Swifte's Heath, home to Jonathan Swift during his school years in Kilkenny. The 'e' was evidently dropped from the name before the satirist gained notoriety as the author of Gulliver's Travels and A Modest Proposal.