The second longest stream in the municipality of Mação, with an approximate length of 23 kilometres.
Its "birth" is somewhere between the villages of Chão de Codes and Vale de Amêndoa, in the middle of the Serra do Bando do Codes.
Its name changes along the way:
- Coadouro, from the source to Monte Penedo;
- Boas Eiras, from Monte Penedo to the Beira Baixa railway line;
- Estação, from the Beira Baixa railway line to its mouth (River Tagus).
100 metres from its mouth, it is crossed by the PR4 MAC Ortiga Sul Path and the GR12.3 Tejo Great Path.