The Aqueduct of the Gier is an ancient Roman aqueduct probably constructed in the 1st century AD to provide water for Lugdunum (Lyon), in what is now eastern France. It is the longest and best preserved of four Roman aqueducts that served the growing capital of the Roman province of Gallia Lugdunensis. It drew its water from the source of the Gier, a small tributary of the Rhone, on the slopes of Mont Pilat, 42 km south-west of Lyon.
Its route has been retraced in detail, following the numerous remains. Leaving the uplands of the massif du Pilat, department of the Loire, the aqueduct hugs the surface relief and crosses the department of the Rhone, passing through Mornant, Orliénas, Chaponost and Sainte-Foy-lès-Lyon to terminate at Lyon.
In its extent, it draws upon the whole repertory of Roman techniques of aqueduct building, taking a slope that averages 0.1%, or a meter every kilometer. There are 73 km of covered ditches laid with a concrete culvert 3 m high and 1.5 m wide, which is sunk as deep as 4 m beneath the land surface. The aqueduct passes through 11 tunnels, one of which, near Mornant, is 825 m in extent. Access for cleaning and repairs was through manholes at 77 m distances. There are some thirty stretches in the open air. There are ten stretches raised on walls and arches, which provide the most spectacular visible remains of the aqueduct.
Four inverted siphon tunnels cross the particularly deep and wide river valleys of the Durèze, the Garon, the Yzeron and the Trion on pipe bridges raised on high arches. In these, water filled a sunken tank tower (castellum) on the brim of a slope. The tank effected a transition between open channel flow and a lead pipeline. From the castellum water was carried, now pressurized, in a set of airtight lead pipes laid side by side, with soldered joints, down the valley slope, across a bridge spanning the river, whose piers and arches are the most notable remains of the system, and up the facing slope, to a tank slightly lower than the head tank, losing just a little hydraulic head in the process. The inverted siphons obviated the bridging of deep valleys with arcade upon arcade of arches, as at Pont du Gard, which marks the limit of such a system.References:
The Château d'Olhain is probably the most famous castle of the Artois region. It is located in the middle of a lake which reflects its picturesque towers and curtain walls. It was also a major stronghold for the Artois in medieval times and testimony to the power of the Olhain family, first mentioned from the 12th century.
The existence of the castle was known early in the 13th century, but the present construction is largely the work of Jean de Nielles, who married Marie d’Olhain at the end of the 15th century.
The marriage of Alix Nielles to Jean de Berghes, Grand Veneur de France (master of hounds) to the King, meant the castle passed to this family, who kept it for more than 450 years. Once confiscated by Charles Quint, it suffered during the wars that ravaged the Artois. Besieged in 1641 by the French, it was partly demolished by the Spaniards in 1654, and finally blown-up and taken by the Dutch in 1710. Restored in 1830, it was abandoned after 1870, and sold by the last Prince of Berghes in 1900. There is also evidence that one of the castles occupants was related to Charles de Batz-Castelmore d'Artagnan, the person Alexandre Dumas based his Three Musketeers charictor d'Artagnan on.
During the World War I and World War II, the castle was requisitioned first by French troops, then Canadian and British soldiers. The current owner has restored the castle to its former glory.