The nuraghe Orolio (or nuraghe Madrone) is made up of a central keep, two side towers on the front and a third at the rear, connected to another two by rectilinear curtain walls eleven metres long.
The circular keep has a diameter at the base of more than 12 metres and a maximum residual height of 11.5 metres.
The ground-floor chamber, bordered by three niches arranged in a cross, and the second-floor chamber of the central tower, including the staircase and the passageway niche, both preserve the tholos roof intact.
The first-floor chamber, with a circular plan and a height of 5.3 metres, is lit by a large rectangular window splayed inwards, surmounted by an architrave and a relieving space.
To enter the tower, a breach in the western part of the keep must be passed through, which leads to the spiral staircase in the entrance corridor, bordered on the right by an elliptical niche.
The entrance to the six-metre high tholos chamber has three quadrangular niches arranged in a cross and a trapezoidal-shaped door.
In the rear wall of this chamber, there is a rectangular opening that leads to a kind of a room at a slightly oblique angle to the entrance. A narrow staircase leads from here in an anti-clockwise direction above the entrance passage to a small domed room, located in the passageway niche and illuminated by a loophole.