Tens of thousands of euro worth of damage is believed to have been caused during a break-in at Christ Church Cathedral in Waterford city.
Christ Church Cathedral is one of the best known buildings in the city. Aoife and Strongbow were married on the site in 1170.
It is understood the ceiling of the building was damaged when those involved in the break-in were trying to gain access to an office through the roof last night.
The ceiling in the church had been restored in 2003.
Rubble from the ceiling fell into the back of the historic Thomas Elliott organ, which dates back to 1817, causing extensive damage. The organ had undergone major restoration in 2002.
The vestry was also ransacked. It is believed those involved in the break-in were searching for money.
The discovery was made this morning when one of the employees arrived for work and noticed the door was open.
It is believed those who broke in gained access through the bell tower and then the ceiling.
Trevor Lester, Dean of Christ Church Cathedral, says there is evidence to suggest that access was gained by cutting a hole in the historic ceiling above the organ.
About €200 was taken from the safe in the raid but Mr Lester said the real cost is the damage done to the historic organ and the building.