There is a whole host of mounds, cairns, passage tombs and things on Tallaght hill to the south west of Dublin

http://www.megalithomania.com/show_site.php?site_id=630

Just 60m from this is a dew pond - almost certainly Bronze Age if not older and part of one mother of a ritual site.

I think myself and Lissy recently discovered one near to this along with a henge:
http://www.megalithomania.com/show_site.php?site_id=469

but I'm waiting for someone to look at them before leaping to any conclusions.