the region that met Roman quality and quantity guidelines were also equipped with aqueducts to feed the main line. Architectural aspects To protect against frost, most of the aqueduct ran about below the Earth's surface. Archaeological excavations show that, at the lowest level, the Roman engineers had placed a loose layer of stones. On this base, they set a concrete or stone U-shaped groove for the water and, over this, cut stones and mortar were used to build a protective arch. For the concrete work and the arch, the engineers used boards to build the form. Impressions of the wood grain remain in the concrete 2,000 years later. The aqueduct had an inner width of and a height of , so a worker could enter the tube when necessary. The outside of the aqueduct was plastered to keep dirty water out. At several locations, a drainage system was set up alongside the aqueduct to keep ground water away. Smaller streams crossed the aqueduct through culverts: one, very near the source, is still well-preserved. The inside of the aqueduct was also plastered with a reddish mixture called opus signinum. This mixture contained lime as well as crushed bricks. This material hardened under water and prevented leakages to the outside. Small cracks were sealed with wood ash, which was strewn over them the first time the aqueduct was set in operation. Roman spring constructions Several springs in the area were fitted with constructions to aid their direction into the aqueduct. The first is at the source, Grüner Pütz near Nettersheim. The most studied is the "Klaus fountain" at Mechernich. This site has been archaeologically reconstructed and preserved. The constructions at the various springs were designed to fit in with the characteristics of the area and would meet today's technical requirements. There were four major areas of springs: Grüner Pütz (Green well) near Nettersheim Klausbrunnen (Klaus spring) near Mechernich An area of springs in Mechernich-Urfey The Hausener Benden in Mechernich-Eiserfey The spring area Hausener Benden, also near Mechernich, is interesting because it was discovered rather late and was put back into use. In 1938, while searching for a drinking water source for Mechernich, the workers encountered the feed line for the aqueduct from this area. The water from the feed was simply connected into the modern water network. So as not to damage the spring, they carried out no archaeological search for the