It measures a full 1150 metres in circumference and has 770-metre-long stone ramparts on three sides. On the fourth side the mountain drops away steeply, so there was no need for ramparts here. The fort is called Träleborg and provided open views over the countryside for many kilometres. The site was part of a chain of signal beacons, which could be lit to pass signals from one to the next. The fort was built around 2800 BCE, and excavations were carried out here in the 1980s.