The monumental gateway, which stood at the northeast corner of the sanctuary, was built by Eumenes II in the early 2nd century BC. The two-storey building, had a porch of four Doric columns (tetrastyle) on the ground floor, above which was a dedicatory inscription by Eumenes to Athena Nikephoros. The upper storey was a balcony with four Ionic columns and fronted by a military frieze depicting armour and weapons. The Sanctuary of Athena Nikephoros, on the southwest corner of the walled citadel on the Acropolis, was one of Pergamon's oldest religious centres, used for the worship of Athena and Nike.