4. Step 4 : Upaix - Ribiers

This stage begins in Upaix, on the banks of the Durance, Provence’s largest river, which flows through four departments, from the Alps to the Crau Plain.
Head south to reach the village of Le Poët, built on the southern slope of a 650-meter-high hill that separates the plain from that of Upaix. The village’s name derives from this hill: Podletum, “the little height.” This has earned it the designation of a hilltop village. It is located on the famous Route Napoléon.
Continue on to Mison. Perched on a rocky promontory, the ruins of the 12th-century Mison castle offer a panoramic view of the surrounding landscapes, notably the Chabre mountain and the Buëch valley. Having once belonged to the Counts of Provence, the castle is now owned by the municipality. Visible from the Méouge Gorges, the fortress occupies a strategic location at the confluence of the Méouge and Buëch rivers. It was home to powerful noble families during the Middle Ages. Today, the site stands out as a prominent landmark and offers a splendid 360° view of the surrounding area. 
Just before reaching Ribiers, the route runs alongside and then crosses the Buëch. The Buëch is a braided river where various channels and gravel bars crisscross, reshaped with every flood, and serve as a source of diverse natural habitats. These habitats are home to a multitude of species, some of which are rare: the Rhône apron, a small fish endemic to the basin of the same name; beavers; numerous bats that find refuge in the old trees lining the river; the white-clawed crayfish; and more...
Continue on to Ribiers, the destination town.