A Las Merindades Ebro tributary rising in the Sierra de Ordunte and joining the parent river at Trespaderne. The Nela is freestone trout water in the Burgos limestone country — clear, partially canopied, with pool-riffle structure through the middle reaches around Villarcayo. Wild brown trout throughout. Best fished from late April through June; the upper reaches above Santelices hold up into July.
- Limestone