Clas an Aifrinn or ‘Mass Rocks’, as they are more commonly known, were hidden locations where Catholic Mass was served using a large flat stone as an altar. Mass Rocks became a popular and important feature to the Catholic religion during the Penal Laws (1695-1829), where Catholics were forbidden from celebrating mass.
The Mass Rock sites were kept secret and look-outs were formed in the event of being caught. The priest was brought to a prominent, flat rock in a small dip or valley to say mass, often under the darkness of the night. If a flat stone was not available, one was taken from a nearby church.
As Catholic Mass was forbidden, there were officers known as ‘Priest Hunters’, who’s sole purpose was to hunt out any priests which were serving mass illegally and in-prison them. This made the look-outs at the Mass Rock sites extremely important. Mass Rocks later became less used as Penal Laws were abolished in Ireland.
At this Mass Rock site in Sylane, there has been an altar and cross erected to commemorate Fr. Ulick Nally, the priest who celebrated Mass there for his people. It is said that, Fr. Ulick Nally evaded capture for many years through posing as a servant in a nearby house.