MACHÆRUS, in Ancient Geography, a citadel on the other side Jordan, near the mountains of Moab, not far from and to the north of the Lacus Asphaltites. It was the south boundary of the Peræa: situated on a mountain encompassed round with deep and broad valleys; built by Alexander king of the Jews; destroyed by Gabinius, in the war with Aristobulus, and rebuilt by Herod, with a cognominal town round it. Here John the Baptist was beheaded (Josephus).