Per my other note just to the north, there is another car park here. It looks brand new. There seem to be EV change points.

Path runs from house as shown, thru a vehicle sized gate then runs s-s-e near the perimeter of the field, as shown then loops around West & then north as shown.

At the southernmost tip there is a spur south-eastwards that seems to join the old road (we didn't investigate).

Per my other notes, the tarmac path runs northward as shown until this point until it stops in the middle of nowhere. You can continue on grass.

If I go back anytime soon I'll take some photos.

There's a new tarmac path for pedestrians in a u-shape around this field, running south from where it joins the existing path - about here - then looping back north on the western side of the field. Looks like the paths are still under construction. This description https://www.dlrcoco.ie/en/parks-outdoors/fernhill-park-and-gardens is out of date.

Should be called Fairy Castle, I think.

Google Maps has this down as 'Fairy Castle'. Also, my copy of Joss Lynam's 'Easy walks near Dublin' (which I trust) has this location as Fairy Castle, and 'Two rock' as the location 500m along the path to the S-E (marked 'Two rock' on this map). The first image here https://en.wikipedia.org/wiki/Two_Rock shows the 2 rocks which I'm guessing are the ones to the S-E.

Sorry I lack the skills (and confidence) to make the change.