Dun an Or! (spelled wrong, I'm certain).

Yes! Atlantis, as it was called by the Greeks, did indeed sit on the Dingle Pennisula! Heavens to Betsey, I've been there, trodden the Sacred Ground, and didn't even know I was!

Dun an Or! The Fort of Gold! It all fits.

And just think -- the part that hasn't fallen into the sea is now a golf course.