Beltxu, Mountain summit in Lower Navarre, France

Beltxu (Belchou in French) is a 1,130 m summit in the Arbailles massif of the western Pyrenees, on the boundary of Hosta and Saint-Just-Ibarre in Lower Navarre. Its broad, rounded top is a limestone dome, mostly covered in snow in the photograph, with only scattered dark points of exposed rock and low vegetation showing through. Beech forest covers the flanks but stops short of the summit, and the Bidouze rises from a karst network on the south-east side.

Beltxu lies on the boundary line between the communes of Hosta and Saint-Just-Ibarre in Lower Navarre, and that line passes exactly through the summit. Access routes run from Hosta via the road to the 712 m Zuharry pass and then on foot, or from Saint-Just-Ibarre along forest paths. The summit carries an out-of-service relay antenna.

The name Belchou probably comes from the Basque beltz, meaning "black"; in Basque the summit is called Beltxu. The mountain remains summer pasture for sheep and cattle, and working kayolars, the shepherds' huts, still stand on its slopes. Écobuage, the controlled burning of vegetation, is still practised there.

The rocky slopes require good footing and care when climbing, especially on loose limestone. Start early in the day and bring weather protection, as conditions on the mountain can change quickly.

The Bidouze rises on the south-eastern side of Beltxu, emerging from a karst network in the limestone. An antenna relay stands on the summit, now out of service, and the site is used for paragliding.