The first emperor of the German Empire was Wilhelm I. Berlin was made the capital city, and Otto von Bismarck was appointed chancellor. Prussia played a key role in the process of unification of Germany. At this time,known asthe Founding Era, Berlin had a population of around 800,000. It is claimed that in 1871, this number exceeded 1 million. Industrialisation was developing rapidly. Interestingly enough, construction of the Berlin underground commenced in 1896, and was completed in 1902. In addition, tenement blocks were built in the neighbourhoods just outside the downtown area, including Berg, Kreuzberg, and Wedding. This economic boom was followed, however, by a decline in the 1870s. Construction of the Reichstag, the building of Parliament, began in 1884.