The archaeological site in Syria that Agatha Christie helped excavate was Tell Brak.
Tell Brak is an ancient settlement in northeastern Syria, in the Upper Khabur region. It was excavated in 1937 and 1938 by British archaeologist Max Mallowan, Christie’s second husband, during expeditions that Christie accompanied and supported.
Christie was not the expedition’s professional archaeologist, but she contributed practical work at the sites, including cleaning, cataloguing and photographing finds. Her experience with excavations and ancient objects later informed her memoir Come, Tell Me How You Live and added archaeological detail to her fiction.
Tell Brak was already a major settlement thousands of years before the classical civilizations associated with Babylon and Ur. It contains evidence of occupation from the Neolithic and Bronze Age, including the distinctive Eye Temple and numerous small eye idols. Nimrud was another site associated with Christie and Mallowan, but it is in modern Iraq, not Syria.