Samhain was one of four significant seasonal festivals in the Celtic calendar. These all centred around important times in nature and farming, heralding the beginning of new seasons and new activities. They were called Imbolc (February), Beltane or Beltene (May), Lughnasadh (August) and Samhain (October).
Samhain marked the end of the harvest and the beginning of winter, the darker half of the year. It was traditionally celebrated on the evening of the 31st October and the 1st November and has now become the modern day Hallowe'en.
Samhain is the time of year when livestock would be brought in from the fields for the winter. It was believed that the boundary between the Otherworld and the land of humans would briefly disappear. This connection with the supernatural is a key feature of the modern day Hallowe'en celebrations. As with many other Celtic festivals, fires would have been lit and feasts were prepared as part of the celebrations.
Oweynagat (The Cave of the Cats) at Rathcroghan in County Roscommon is an underground structure or "souterrain". It features in many Celtic stories and some tell of it opening up at Samhain, becoming a gateway for mystical beings to traverse from the Otherworld into the land of humans. It was said to be the home of the famous Morrigan, a powerful female figure within Celtic mythology, capable of changing shape into a variety of animal forms.