Montsec and Congost de Mont-rebei

The Congost de Mont-rebei is probably the most spectacular river canyon in all of Catalunya and one of the most impressive on the entire Iberian Peninsula. Carved over millions of years by the Noguera Ribagorçana river through the Sierra del Montsec, it forms a gorge 500 metres deep with vertical walls so narrow that in some spots they barely let sunlight through. The wooden walkway bolted to the vertical cliff face (which you walk, not ride) is one of the most vertigo-inducing hiking experiences in Spain: you are literally walking 200 metres above the turquoise river water, gripping an iron railing fixed into the rock.

The canyon marks the natural boundary between Catalunya and Aragón, and for centuries it was virtually impassable — only a handful of shepherds knew the routes across it. The current walkway was built in the early 20th century by workers constructing the Canelles hydroelectric dam, and was later converted into a hiking trail. To reach the trailhead by motorbike, ride to the Masieta or Mas Carlets car park, leave the bike, and walk between one and two hours depending on the route you choose.

The Sierra del Montsec, home to the canyon, has a remarkable environmental distinction: it is one of the areas with the least light pollution in all of Western Europe, making it a premier destination for astrotourism on the continent. The zone is officially designated a UNESCO Starlight Tourism Destination, and in the village of Àger a public astronomical observatory has been set up with professional-grade telescopes for visitors. Moonless nights on the Montsec, under an absolutely black sky with the Milky Way visible to the naked eye in all its splendour, are an experience that is hard to come by in modern Europe.

Àger, the logical base for exploring the area, is a tiny medieval village — barely 600 inhabitants — but with a remarkable history. It preserves the imposing ruins of the Colegiata de Sant Pere, a Romanesque-Gothic church from the 11th century whose founding is attributed to Arnau Mir de Tost, one of the Catalan counts who conquered the most territory from the Muslims during the 11th century. The collegiate church was destroyed in successive wars, but the ruins survive at the top of the village and form one of the most fascinating medieval archaeological sites in western Catalunya. The view from the church spans the entire Montsec and the Vall d'Àger.

Practical riding notes: the approach roads to Mont-rebei are technical but in good condition, with continuous curves and very little traffic. The LV-9047 running along the Camarasa reservoir is especially enjoyable to ride. Fill up in Balaguer or Tremp before heading into the area — inside there is only one petrol station in Àger and another in Areny de Noguera (on the Aragonese side of the canyon). The best season runs from March to June and September to November: in high summer the canyon gets brutally hot. One thing to note: the Mont-rebei walkway has a limited capacity and during peak season you need to book your entry online in advance. For a meal, Restaurant Cal Met in Àger serves honest Catalan cooking at very reasonable prices. And for those who love the night sky: if you stay overnight in the area, take the bike out at 1 a.m. to a remote viewpoint and look up. You will see more stars than you can count.