MACHÆRUS, in Ancient Geography, a citadel on the other side of Jordan, near the mountains of Moab, not far from and to the north of the Lake Asphaltites. It was the south boundary of the Peræa, and situated on a mountain encompassed round with deep and broad valleys, being built by Alexander king of the Jews. It was destroyed by Gabinus in the war with Aristobulus, and rebuilt by Herod, with a town of the same name around it. Here John the Baptist was beheaded.