This museum is a colossal construction, which used more than 25,000 tons of concrete, or 10,000 cubic meters, that is why it requires deep and solid foundations. The foundation was laid on reinforced concrete piles driven into the bedrock at an average depth of 14 meters. The building is based in the clay of the bed of the nearby river “Ria de Bilbao”; therefore, it was necessary to implant piles in large numbers, driven into the ground by many boring machines. In total, 665 pilings were driven to anchor the building to the ground. The base of the building is covered with beige limestone from the Huéscar quarries near Granada, cut from 5 cm thick slabs. The building is clear thanks to the walls, specially treated to protect the interior from the effects of the sun. The glass of the windows has also been treated to prevent light from damaging the exposed pieces. It is clad in titanium plates, arranged in scales, on a galvanized steel structure. The Museum's exterior skin is made of 33,000 titanium plates, a material that has been used to replace copper or lead because of their toxicity. Many tests have been carried out with different materials to find one that would withstand heat and bad weather, while maintaining its character. It was during this research process that tests were started on titanium samples and the best treatment was found. Its lamination process is delicate and has to be done in places with high energy sources, that's why the laminated parts were made in Pittsburgh, in the United States, the rolling allowed to obtain titanium plates only 0.4mm thick, which is much thinner than if we had to use steel plates. Moreover, titanium is about half the weight of steel, indeed, the museum's titanium coating represents only 60 tons. During the conception, the pieces were designed to resist the bad weather, that is why a quilted rather than undulated shape was privileged, to resist the wind, and to avoid vibrations during storms. Titanium is a low-polluting material, and each part has been designed differently according to its orientation on the building, so they correspond perfectly with the curves desired by Frank Gehry. In the fall of 1993, architects at Gehry Partners began to utilize Dassault Systemes' CATIA software for the schematic design phase of the Guggenheim Museum Bilbao to digitize and model the exterior of the Museum project. Essentially, this software calculates point by point the stresses to which materials are subjected, by generating a 3D model showing the different tensions and allowing the values of many structural elements of the museum to be calculated: the steel structure, titanium cladding or foundations, among others.