November 10th, 1990. The base Tower island, situated in the midstream of the Seine river. In the foreground: the piles that are 54 meters deep (equivalent to 18 floors of a building), are pushed into the riverbed by a large machine. Within each tube the woil will be removed, and metal cages will be lowered within the tubles. The metal cages form the skeleton around which the concrete will be poured. Around these metallic structures, there will be smaller tubes, used to guide ultra sound detectors to check if each of the concrete layers are spread evenly and that there are no imperfections. Inch by inch, each section is double checked with a sound detector, looking for cracks or errors. The German engineer said that the security control methods were outstanding. This photo shows the metallic cages before they are inserted into the empty tubes, and covered with cement fillings.