This National Monument is St Mary’s Cathedral. It is located on Bridge Street in Limerick City and dates back to 1168 making it the oldest building in Limerick City predating John’s Castle. This was previously a Viking meeting place called a ‘Thingmote’ dating to c.970 a.d and was their most westerly European stronghold  It was then the site of Donal Mor O’Brien, the last King of Munster’s palace who founded the church. Experts believe that the great west door is the original main entrance to his royal palace. The stones around this doorway are marked by indentations that were used by defenders of the city to sharpen their swords and arrows during the many sieges of Limerick. The interior to the Cathedral is truly magnificent with thick rustic stone arches and beautiful tracery in the windows. In the 14th century, the tower which rises to 120 feet was added. In 1651, Cromwellian forces used the Cathedral as a stable and removed it’s 13 ft pre-reformation high altar. This was the largest altar of it’s kind carved from a single limestone block in all of Ireland and the UK . This altar was only reinstated in the 1960s.