Côte de Trieu

Côte de Trieu is a modest hill straddling the border between Belgium's two main regions — Wallonia and Flanders — in the municipality of Mont-de-l'Enclus, in the province of Hainaut. In Dutch it goes by the name Knokteberg. Despite its unassuming height (the summit tops out at just 141 metres above sea level), the climb has earned lasting recognition thanks to one of the world's most famous cycling races: the Tour of Flanders (Ronde van Vlaanderen).

Where exactly is Côte de Trieu?

The road that forms the Côte de Trieu climb runs along the south side of the Kluisberg, one of the hills making up the Flemish Ardennes (Vlaamse Ardennen), a range stretching across the southern edge of the province of East Flanders, right up against the Walloon border. The summit of Côte de Trieu marks the administrative boundary between the municipalities of Mont-de-l'Enclus and Kluisbergen — and, by extension, the linguistic and regional border between French-speaking Wallonia and Dutch-speaking Flanders.

Why is this spot known among cyclists?

In cycling circles, Côte de Trieu is almost always mentioned together with the neighbouring Kluisberg — it offers the shortest route for a race to leave Wallonia and re-enter Flanders. There's a small naming quirk worth noting: since the hill technically sits in Wallonia, the French name Côte de Trieu would be the correct one, and that's indeed how it's listed in another Belgian race, Het Volk. The organisers of the Ronde van Vlaanderen, however, stick to Flemish naming conventions even though the climb itself lies on the French-speaking side of the border.

The climb's profile is distinctive: the road rises gently at first, winding through open farmland with no sharp gradient changes. Only in the final stretch, just before the summit, does the gradient noticeably steepen — and it's precisely there that the road crosses the border and re-enters Flemish territory.

What else is worth knowing about the area?

Côte de Trieu sits right next to the Kluisberg, a hill complex that forms part of the Flemish Ardennes, a region famous for its dense network of steep, cobbled climbs used in the spring cycling classics. A few kilometres away rises the celebrated Oude Kwaremont — not a separate hill, but the name of one of the cobbled roads leading up the Kluisberg itself. The Oude Kwaremont is considered the longest cobbled climb in the history of the Ronde van Vlaanderen, and since the race's route overhaul in 2012 it has become one of the decisive sections of the entire event.

Who is this place for?

Côte de Trieu will appeal in particular to road cycling enthusiasts and anyone following the history of the Flemish classics — a place where an administrative border, a linguistic border, and a sporting landmark all converge on a single modest hill among the fields of the Flemish Ardennes. It also makes a worthwhile stop for anyone planning a cycling route that follows the region's legendary climbs, linking Côte de Trieu with the nearby Kluisberg and Oude Kwaremont. Beyond its sporting significance, the surrounding area offers a quiet, rural landscape typical of the Wallonia–Flanders borderland: gentle slopes, farmland, and small villages tucked into this corner of southern Belgium.

Frequently asked questions

Are Côte de Trieu and Kluisberg the same hill? No — they are neighbouring hills. The Côte de Trieu road runs along the south side of the Kluisberg and climbs to its summit from the Walloon side.

How high is Côte de Trieu? Its summit sits at 141 metres above sea level.

Is it the same climb as the Oude Kwaremont? No. The Oude Kwaremont is a separate, cobbled road up the Kluisberg, known as one of the key sections of the Ronde van Vlaanderen since 2012.