It is a quartzite outcrop that crosses the Pisão river from side to side, split in the middle, where the river passes.
A wall was built on top of it in opus caementicium, lined with stone on both sides.
Currently, two segments remain.
The right side of the river was destroyed for the construction of Nacional road 2 and even the left side was used as a quarry for the construction of the bridge over the river.
The dam would be 5m high and its basin 1km long.
The water flowed towards the Milreu area, leaving on its left side, through a still visible channel, excavated in the rock.
It would serve to feed the gold explorations that exist in large quantities in the Codes river.