Hatra is the richest archaeological site in the Parthian Empire known to date and has great potential for a better understanding of this enigmatic empire and its relationship with Rome. After an introduction to this little known site, seventeen contributions written by leading experts in the field provide the reader with the latest insights into this important late-Parthian settlement. They touch upon three themes. The first section, ""Between Parthia and Rome"" contains three articles that discuss the relationship between Parthia and Rome on the one hand, and Parthia and its vassal states on the other.