Inhab­it­ed since the 2nd cen­tu­ry A.D., Quirigua had become dur­ing the reign of Cauac Sky (723–84) the cap­i­tal of an autonomous and pros­per­ous state. The ruins of Quirigua con­tain some out­stand­ing 8th-cen­­tu­ry mon­u­ments and an impres­sive series of carved ste­lae and sculpt­ed cal­en­dars that con­sti­tute an essen­tial source for the study of Mayan civ­i­liza­tion.