Most Muslim graves are traditionally simple and unadorned, but in North Africa the graves of important figures were often covered in a domed structure (or a cupola of often pyramidal shape) called a "qubba" (also spelled "koubba"). This was especially characteristic for the tombs of "saints" such as "wali"s and marabouts: individuals who came to be venerated for their strong piety, reputed miracles, or other mystical attributes. Many of these existed within the wider category of Islamic mysticism known as Sufism.