Navan is supposed to take its name from Emain, twin, and, Macha, a goddess, whose name is also incorporated in Armagh (Ard Macha) 2.5km to the east. In the Táin Bó Cúailgne, Navan is portrayed as the seat of Connor Mac Nessa, the legendary king of Ulster, leader of the Red Branch Knights, and protector of the youthful hero Cú Chulainn, who single-handedly caused the retreat of the Connaught forces.

The hilltop is encircled by a substantial ditch and outer bank forming a ceremonial enclosure. This was constructed about 100BC. About the same time a large mound was constructed on top of the hill. Excavations here found a timber structure 40m in diameter comprised of 5 rings of large oak posts, some 280 altogether. At the centre was a very large post, some of the wood of which survived and was dated to 95BC. Shortly after, while the structure was still standing, a cairn of boulders was constructed within it. The timber building was then burned deliberately, and the surviving cairn was capped by the mound of turves that can be seen today.