Kerbstone 15, a striking Neolithic artifact from the Knowth passage tomb in Ireland, is decorated with intricate carvings of spirals, U-shaped motifs, and a central cupmark surrounded by 20 radiating lines.

It is one of 124 kerbstones that encircle the site’s great mound, forming part of the largest concentration of megalithic art in Europe.

Though some scholars suggest the stone may have functioned as an ancient calendar, the true meaning of its symbols remains uncertain. A testament to Neolithic artistry, Kerbstone 15 provides a rare window into the symbolic and spiritual world of a long-vanished culture.