From the Wiki:
Before Christianization, the
Gaels, as with other Celts, practiced polytheistic rites with a variety of gods and goddesses. They were also
animists, believing that all aspects of the natural world contained spirits, and that these spirits could be communicated with. Gaels practiced four religious festivals a year:
Imbolc,
Beltaine,
Lughnasadh and
Samhain. These festivals were equidistant from each other, and divided the year into four quarters. Rather than building temples, the Gaels often performed rituals in sacred groves known as
nemetons.
Click to view