There is nothing hidden at the posted co-ordinates.
To find this cache you must complete the nearby 5 stage Adventure Lab DUBLIN CITY WALLS.
The Adventure Lab will take you on a short tour of some of the surviving sections of the old medieval city walls. The image revealed on completion of each stage is an artists impression of how that location might have looked in medieval times.
Each completed stage will reveal 2 numbers and 2 letters, eg. A-1, B-2.
Replace the letters in the following formula with its associated number to reveal the final location:
N 53 AB.CDE W006 FG.HIJ
Use your phone's native QR code scanner or download an QR reader app to open this adventure in the Adventure Lab mobile app, or use the following URL:
https://labs.geocaching.com/goto/Dublin-Walls
For the final I would suggest finishing up at either City Hall or St Audens Gate.