geological history between five and a thousand million years: the crystalline basement of the Aarmassif and Gotthard Massif mountain ranges, the Helvetic and Penninic nappes, the Southern Alps, the limestone of the Jura Mountains, and the molasses of the Swiss Plateau. The elaborate handling of these rocks is unique in the history of Swiss architecture. Auer also planned the rest of the design of the Federal Palace, personally selecting most the 38 Swiss artists who carried out the work and obliging them to work according to his detailed specifications. His approach corresponded to that of his teacher Theophil Hansen, who had also drawn up and rigorously enforced an iconographic program for the parliament building in Vienna. Auer did not have a free hand in selecting the all the artists. Federal Councillor Adrien Lachenal, whose Federal Department of Home Affairs was responsible also for construction and art, awarded some commissions because he felt too little consideration had been given to French-speaking Switzerland. 173 Swiss companies were involved in the construction work. Auer created a Swiss national monument with a rich and symbolic iconography depicting the history, constitutional foundations, and activities of the country's inhabitants. The Swiss Confederation bought the casino property from the city, after which construction began on the parliament building on 5 September 1894. The Federal Terrace on the south side was extended, but not all the way to the as originally planned. On 11 April 1900, the erection of the large dome was celebrated. The handover of the parliament building took place on the morning of 1 April 1902 in an official ceremony. The construction costs for the parliament building amounted to 7.2 million francs (about 700 million in today's terms). Of this, 16.2% was spent on artistic decoration. Structural changes After the opening of the parliament building, the two council chambers in Federal Palace West were abolished; their original use can only be guessed at. Instead of the Council of States hall, offices and a post office counter were built (in operation until 2005). The former National Council Chamber was reduced in size and further subdivided by an iron construction with stairs and walkways. It has since housed a library for use by employees of the federal administration and members of parliament, which is not open to the public except for special occasions, for security reasons. Over the course of time, the use of space in the