Ancient Ireland, known for its rich history, was inhabited by Celtic tribes around 600 BC. These tribes spoke the Irish language and practiced a polytheistic religion, worshipping various gods and goddesses. They lived in small communities, often in circular houses made of wood and thatch, and relied on farming, hunting, and fishing for sustenance. The arrival of Christianity in the 5th century AD marked a significant change in Ancient Ireland. Monasteries, such as Clonmacnoise and Glendalough, became centers of learning and culture. The famous Book of Kells, an illuminated manuscript, showcases the artistic achievements of this period, blending Celtic and Christian traditions.