HIRA, capital of old Arabian kingdom of Lakhmid dynasty, 4 m. S.E. of modern Najaf in `Iraq, founded 2nd century B.C. Practically subordinate to the Sasanian empire, this kingdom, comprising the Euphrates valley and upper part of the Persian gulf, constituted a buffer State towards Arabia. After the battle of Qadisiya (637) and, the founding of Kufa by the conquering Arabs, Hira rapidly fell into decay, and its ruins do not suggest that it was ever of any architectural merit.