Answer by taking a quote from the following article:

Dame Agatha Mary Clarissa Christie, Lady Mallowan,  (nee Miller; 15 September 1890 - 12 January 1976) was an English writer. She is known for her 66 detective novels and 14 short story collections, particularly those revolving around her fictional detectives Hercule Poirot and Miss Marple. Christie also wrote the world's longest-running play, a murder mystery, The Mousetrap, and six romances under the name Mary Westmacott. In 1971 she was appointed a Dame Commander of the Order of the British Empire (DBE) for her contribution to literature.

Christie had a lifelong interest in archaeology. She met her second husband, Sir Max Mallowan, a distinguished archaeologist, on a trip to the excavation site at Ur in 1930. But her fame as an author far surpassed his fame in archaeology. Prior to meeting Mallowan, Christie had not had any extensive brushes with archaeology, but once the two married, they made sure to only go to sites where they could work together. Christie accompanied Mallowan on countless archaeological trips, spending 3-4 months at a time in Syria and Iraq at excavation sites at Ur, Nineveh, Tell Arpachiyah, Chagar Bazar, Tell Brak, and Nimrud. She wrote novels and short stories, but also contributed work to the archaeological sites, more specifically to the archaeological restoration and labelling of ancient exhibits, including tasks such as cleaning and conserving delicate ivory pieces, reconstructing pottery, developing photos from early excavations which later led to taking photographs of the site and its findings, and taking field notes.  Christie would always pay for her own board and lodging and her travel expenses so as to not influence the funding of the archaeological excavations, and she also supported excavations as an anonymous sponsor. During their time in the Middle East, there was also a large amount of time spent travelling to and from Mallowan's sites. Their extensive travelling had a strong influence on her writing, as some type of transportation often plays a part in her murderer's schemes. The large amount of travel was reused in novels such as Murder on the Orient Express, as well as suggesting the idea of archaeology as an adventure itself.  After the Second World War, she chronicled her time in Syria with fondness in Come Tell Me How You Live. Anecdotes, memories, funny episodes are strung in a rough timeline, with more emphasis on eccentric characters and lovely scenery than on factual accuracy. From 8 November 2001 to 24 March 2002, The British Museum had an exhibit named Agatha Christie and Archaeology: Mystery in Mesopotamia, which presented the life of Agatha Christie and the influences of archaeology in her life and works.

What other sites did she visit?
Christie accompanied Mallowan on countless archaeological trips, spending 3-4 months at a time in Syria and Iraq