Gardai in Dublin are investigating the theft of 24 metres of historic granite from Victoria Quay, which was being restored by contractors for Dublin Corporation.
The 200-year-old granite, valued at up to £15,000, was stolen overnight on Tuesday.
Gardai at Kevin Street said the thieves would have required lifting equipment and a lorry to remove the granite, which was stored behind barriers.
"A considerable amount was taken," said a Garda spokesman. "We are appealing to anyone in the area near St James's Gate on Tuesday night/Wednesday morning who might have seen something to come forward."
A spokeswoman for contractors Wallace Construction described the stone as priceless. "It can't actually be replaced. It would need to be weathered the same as the rest of the quay."