Río Onin Gorge & Watermill Trail
Just minutes from the town centre, the Río Onin carves a narrow limestone gorge draped in ferns and ancient beech before widening into a series of mill pools where Lesaka's medieval grain and textile mills once hummed. The riverside trail is one of the most rewarding short walks in the Navarrese Pyrenean foothills.
The trail itself
The signposted path begins at the edge of the old quarter, drops quickly to river level and follows the Onin upstream for roughly 4 kilometres through increasingly wild terrain. The gorge narrows to just a few metres at its tightest point, where the water turns a deep jade green over limestone slabs — a natural swimming spot that locals keep deliberately quiet.
Along the way you pass the skeletal stone remains of at least three watermills, their millstones still visible amid the undergrowth. Interpretive panels (in Spanish and Basque) explain how the mills powered Lesaka's 17th-century textile economy.
Wildlife and best seasons
The gorge is a reliable spot for dippers — the small, bobbing brown birds that walk underwater to feed — and grey wagtails flitting between river boulders. In May and June the riverbanks are thick with wild garlic and the beech canopy is at its most luminous, filtering light into shades of lime and gold.
After heavy autumn rain the river runs fast and the waterfalls above the gorge are at their most dramatic. Summer is ideal for paddling in the mill pools; bring water shoes as the limestone is slippery.
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