 Under the direction of the German Archaeological Institute, excavations at Hattusa have been under way since 1907, with interruptions during the world wars.Kültepe was successfully excavated by Professor Tahsin Özgüç from 1948 until his death in 2005.Smaller scale excavations have also been carried out in the immediate surroundings of Hattusa, including the rock sanctuary of Yazılıkaya, which contains numerous rock reliefs portraying the Hittite rulers and the gods of the Hittite pantheon.