A SACRED TREE was known as a “bile” [bʲilʲə] in Old Irish. It was often a sacred tree, of great age, growing over a holy well or fort. Five of them are described in the Dindsenchas, and one was an oak, which not only yielded acorns, but nuts and apples.
Hill of Tara, Meath, Ireland...The Holy Well at the Hill of Tara. The Hill of Tara was the ancient capital of Ireland, where the High Kings were crowned and probably the most sacred spot to Irish pagans before the arrival of Christianity
A couple of miles north of Penzance, and at the end of a winding muddy path, Madron Holy Well is thought to date from pre-Christian times and is still visited by passers-by. The well is easy to find, with signposts and more traditional 'clouties' - pieces of rag tied to the tree according to traditional custom at healing wells.