States of Austria arable terrain. The other five states, in contrast, are located in the Alps and thus are comparatively unsuitable for agriculture. Their terrain is also relatively unfavourable to heavy industry and long-distance trade. Accordingly, the population of what now is the Republic of Austria has been concentrated in the former four states since prehistoric times. Austria's most densely populated state is the city-state of Vienna, the heart of what is Austria's only metropolitan area. Lower Austria ranks only fourth with regard to population density even though it contains Vienna's suburbs; this is due to large areas of land being predominantly agricultural.
Germany–United States relations exchange programs and projects, and focus on space exploration, the International Space Station, environmental technology, and medical science. Import cooperations are also in the fields of biochemistry, engineering, information and communication technologies and life sciences (networks through: Bacatec, DAAD). The United States and Germany signed a bilateral Agreement on Science and Technology Cooperation in February 2010. In the post-war era, a number of institutions, devoted to highlighting American culture and society in Germany, were established and are in existence today, especially in the south of Germany, the area of the former U.S. Occupied Zone. Today, they offer English courses as