Rome, Constantinople, Hibernia?

Back when I was a kid I had this weird idea that there had been a Roman emperor who planned to take Ireland, and then build a third capital of the Roman Empire in Ireland, on the Atlantic coast.

Can't tell you where I got this idea from. I had a number of strange notions like this.

I've googled around on this question, no luck. Can anyone tell me, was I on target about this, or was it just some bizarre idea floating to me out of the ether?