The Vyerwa valley, located between the city of Ngozi and the Buye Complex, is a sacred valley where the cult of ancestors (kubandwa), a former religious cult was practiced in Burundi and in the Great Lakes region. The importance of this cult seems partly related to the abundance of the kaolin, a product used by the traditional priests known as ibishegu vya Kiranga, during the ceremonies of healing or initiation. Only insiders could go extract this famous kaolin.