St Mary’s Cathedral dates back to 1168 making it the oldest building in Limerick City predating King John’s Castle. This was previously the site of a Viking meeting place called a ‘Thingmote’ dating to c. 970 AD and was their most westerly European stronghold. It then became the site of Donal Mor O’Brien’s palace who was the last King of Munster. 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 its 13-foot pre-Reformation high altar that was made from a single block of limestone. This was the largest altar of its kind in Britain and Ireland. This altar was only reinstated in the 1960s.