There has been widespread anger after Limerick's Treaty Stone monument was targeted in a graffiti attack.
Photos, posted online by Limerick Live 95 FM, show the landmark at the Clare end of Thomond Bridge, covered in blue paint.
The pictures were sent to the local station by a listener and they were met with outrage online.
Local councillor Daniel Butler (FG) said: "Absolute disgrace. Angered & appalled an iconic symbol of our treaty city is treated with such disrespect. Let's as a city find the culprit!"
Reporter Carol Byrne tweeted: "Terrible to see such vandalism to Limericks iconic treaty stone." And local historian Sharon Slater asked: "The purpose of this vandalism is to what?! There is no protest here, just destruction of an iconic #Limerick symbol."
Shortly after 10.30am Limerick Civic Trust confirmed that their team was on the scene cleaning the monument.
A garda spokesman confirmed to Independent.ie that they are investigating the incident: "The Treaty Stone at Clancy Strand, Limerick was damaged overnight 7th/8th March 2017. It appears that blue paint was daubed on the stone. No other damage was caused .
"Investigations are currently underway by the Gardaí at Mayorstone in Limerick."
Traditionally it is said that it was on this rock that the Treaty of Limerick was signed in the sight of both armies at the Clare end of Thomond Bridge on October 3, 1691.
The treaty marked the surrender of the city to the army of William of Orange. Under the terms, a promise was made to respect Catholicism, but the treaty was rejected by the English and Irish Parliaments and its terms were ignored. Thus Limerick became known as The City of the Broken Treaty.
The stone now rests on a pedestal that was first erected in May 1865 by the then mayor of the city John Rickard Tinslay.