From its almost 250 metres high strategic outlook on Cabu Abbas, it kept watch for enemy ships, its view over the horizon stretching all the way to Tavolara island. The Riu Mulinu nuraghe is one of the best known Nuragic fortifications in the northern part of the island. It rises just a few kilometres from Olbia and dates to 1300-1200 BCE. The main tower is well protected by a great 220 metre long wall that encircles the hilltop with widths and heights of up to five metres at some places. What distinguishes this wall is that it envelopes rocky outcrops along its perimeter. There are two entrances, a southern and a northern. Inside is a circular tower with a diameter of about eight metres.