From Porto do Son, take the CP-7102 road to the parish of San Fins de Ribasieira.  Head to the Madalena church and from there up towards As Trabes. After roughly 10 minutes you will come to several viewpoints over the waterfalls.

There are various waterfalls on the River Sieira, the highest of which is 15-20 metres high whilst the other two are 10 and 4 metres high, respectively.