Volker Kästner, “The Architecture of the Great Altar of Pergamon,” in Koester, ed., Pergamon, pp. 137–161, esp. p. 140. Debate continues, however, about whether the construction of the altar was begun in the early, middle or late part of his reign (Radt, “Recent Research in and about Pergamon,” pp. 20–22; Kästner, “Architecture of the Great Altar,” pp. 140–141). The “middle” dating is the most likely, that is, in the 170s B.C.E., a peaceful decade following upon Eumenes II’s victories over the Celts (Gauls) (Kästner, “Architecture of the Great Altar,” p. 140).