If you want to know a little bit more about dark ages Ireland - I suggest reading How the Irish Saved Civilization by Thomas Cahill. It's essentially about the flowering of Irish literary culture (or rather, their newfound ability to copy classical literature), at the very same time that Rome was falling. The book continues to follow the Irish civilization up until about the time of the Viking invasions.
For immediate help, I'm sure I don't know much about 700 C.E., but in the fifth century, some of the important Irish places (I can't remember which ones were towns and which ones were religious sites), were Tara, Cruachan, Uinsnech, and Cashel. The Irish were relatively safe until the viking invasions later on, so it's probably safe to say that at least some of these places survived into the seventh century.