 He was a curator at the Netherlands National Museum of Antiquities between 1990 and 2009 and has directed and been involved with excavations in Syria, Turkey, Germany and Bulgaria.His most important work has been on the Pre-pottery Neolithic B, Neolithic, Halaf and Bronze Age site of Tell Sabi Abyad, including surveys of the Balikh Valley area in northern Syria.He published an extensive compilation of Syria's archaeology with Glenn M. Schwarz in 2003 entitled ""The Archaeology of Syria".