Circle of days by Ken Follett

A PRIESTESS WHO BELIEVES IN THE IMPOSSIBLEA MONUMENT THAT WILL DEFINE A CIVILIZATIONIn the high summer heat, Joia watches the Midsummer ceremony that signals the start of a new year, enthralled. She dreams of a miraculous new monument, raised from the biggest stones in the world.

It is a vision of a great circle, assembled by the divided tribes of the Great Plain. Helped by Seft, a talented miner, it will become their life's work. But as drought ravages the earth, mistrust grows between the herders, farmers and woodlanders.

And an act of savage violence leads to open warfare.