The Gorge du Verdon, also known as the "Grand Canyon of Europe", lies in the mountains of southeastern France.

The canyon runs for 20km (13mi) between the medieval towns of Castellane to the east and Moustiers-Ste-Marie to the west.

Cliffs more than 700m (2,300ft) in height rise on each side of the turbulent waters of the Verdon River. Bare stone walls flank the river at the water's edge, where the gorge narrows to as little as 6m (20ft), then widens again to 100m (330ft). The naked limestone gives way to scrub and bushes above the winter flood line. The span varies between 200m (660ft) and 1.6km (1mi) at the top of the gorge.

A multitude of caves opens out onto the wall of the gorge. These were created when acid from rain ate away bits of limestone. The small amounts of carbon dioxide gas that rain collects as it falls through the air turn it into carbonic acid, which dissolves away calcium carbonate, limestone's chief constituent.

This honeycombing of the limestone has weakened the whole rock area, making it easier for the river to cut its downward path. Geologists think that, before the Verdon Gorge was formed, the river flowed through an underground cavern. Chemical erosion slowly weakened the roof of this cavern. Eventually the roof collapsed under its own weight, opening up a great chasm. The river would have washed away the massive volume of debris generated by such a fall, leaving behind the gorge as it stands today.

The Surrounding Area

Before it reaches the spectacular series of gorges, the river flows southward into the town of Castellane from a clear blue lake that is around 9.6km (6mi) long. It was created by the Castillon Dam, which was built for hydroelectric purposes in 1947. In the town itself, the waters hurry beneath Le Roc, a solitary pinnacle around 183m (600ft) high and capped by a tiny chapel dedicated to the Virgin Mary.

When viewed from the top of Le Roc, the river disappears between the perpendicular walls of the gorges' narrow entrance. A road offering breathtaking views from a number of vantage points has been built around the Verdon Gorge. One of these is Les Balcons de la Mescla, a natural balcony on the southern wall that overlooks the mescla, or "mixing," of the Verdon's waters with those of a tributary, the Artuby. A series of granite ledges tinted in shades of red or yellow ochre form the walls opposite the balcony.

Beneath the balcony, the Verdon abruptly changes course toward the northwest from its previous southward direction. The Corniche Sublime, a mountainous road built high up on the south side of the canyon in 1947, winds in and out of tunnels, bringing travelers to further vantage points, such as Les Falaises des Cavaliers and Le Col d'Illoire.

At the western end of the gorge, the river flows into the arti¬ficial lake of Sainte-Croix. It was 1973, at the same time as the Rue des Crêtes along the north wall of the gorge. The lake's 2,500 hectares (6,667 acres) are mostly used for recreational purposes. The town of Moustiers-Ste-Marie, said to be the most beautiful in Provence, lies to the north of the lake.

In 1905, the French pot-holer and speleologist EA Mattel became the first man to explore the length of the Verdon Gorge.

The River

The waters of the Verdon appear almost turquoise in the full glare of sunlight. However, while the waters are free of soil and organic debris, they are not clear. As the river flows through the gorge, it has an almost milky appearance.

The green translucence of the river originates at Mount Pelat, the river's source. A combination of direct pressure and below-freezing temperatures causes the snowfields and glaciers of the Alpes Maritimes to erode the underlying rock. The resulting pulverized rock is washed into the Verdon where it is held in suspension as fine particles. The physical interplay between the sun's rays and the fine particles conspires to reflect only the green-blue part of the visible spectrum.

Tall rocks that stand up from the center of the riverbed stir the gorge's torrent into long streamers of white water, con¬trasting sharply with the Verdon's delicate shade of green.

Over 2,000 years ago, the unusual color of the Verdon inspired a religious cult among the Vocontii, the dominant tribe of Ligurian Celts who ruled the region. The Vocontii worshipped the Goddess of the Green Waters. They are believed to have hurled offerings to the goddess into the river.