Paul uses the hapax legomenon ίλαστήριον in Romans 3:25. Pauline scholars have discussed the background for Paul’s use of the word, whether from the LXX, Second Temple practice or pagan inscriptions. Two altars were found in the Asian city of Metropolis in the early 1990s with the dedication Καίσαρος ἱλαστηρίου. This article discusses their discovery, the history of Metropolis and the possible relationship of Paul to the city. It explores the date of the erection of the altars by establishing a (...) viable sitz im leben early in the reign of Augustus. It then traces the semantic history of the ίλαστήριον and attempts to establish its possible meaning within Pauline theology. Finally, the question whether ίλαστήριον should be added to the vocabulary of imperial ideology in Paul’s writings is addressed. (shrink)