Gole del Rio Sass: The Secret Basalt Canyon of Val di Non

The Val di Non is the valley of apple orchards. From the windows of the train running through it, rows of apple trees follow one another in orderly lines along the slopes for kilometers. Beneath this agricultural surface, the valley hides a surprising geology: volcanic basalts, erosion-carved gorges, canyons that seem to belong to another landscape. The Rio Sass is the most spectacular of these phenomena — a stream that has cut through ancient lava flows for centuries, leaving vertical walls of black rock up to 30 meters high.

The canyon and the walking route

The Rio Sass forms a gorge of about 2.5 kilometers, walkable on a route equipped with cantilevered metal walkways and steps carved into the rock, safely open since 2001. The canyon is located in Fondo, in the municipality of Borgo d'Anaunia — not in Cles, as sometimes reported — and the guided visit lasts about two hours and requires booking. The basalt walls create a humid, cool microclimate even on the hottest days: bring a sweater even in July.

An ancient rock gorge

The canyon walls preserve geological traces unusual for a volcanic area: fossils, stalactites and stalagmites formed in the rock cavities over millennia. Visits are organized by the Consorzio Smeraldo of Fondo, which manages the route and its seasonal upkeep.

The Val di Non and the castle of Cles

Cles, the capital of the Val di Non, lies further down the valley than Fondo and is also reachable from Trento by car along the SS43, in about 45 minutes: a town of 7,000 inhabitants with a medieval arcaded square and the Palazzo Assessorile, frescoed in the sixteenth century as one of the finest examples of provincial Renaissance painting in Trentino. The castle of Cles, partially open to visitors, overlooks Lake Santa Giustina — an artificial reservoir that covered the old medieval center, whose remains appear during extreme droughts.