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.
Concordats with individual states of Germany successor states. Baden signed its concordat in 1932. The Reich's Concordat, later affirmed as valid by West Germany in 1957, applied some features of Baden's concordat to Hesse, Württemberg and the Diocese of Meissen, which then comprised all of Saxony and parts of Thuringia. Other German states with concordats are Baden-Württemberg (1932), Bavaria (1817–1924), Brandenburg (2003), Bremen (2003), Hamburg (2005), Lower Saxony (1965-1973-1989-1993), Mecklenburg-Vorpommern (1997), North Rhine-Westphalia (1929-1956-1984), Rhineland-Palatinate (1929-1969-1973), Saarland (1929-1975-1985), Saxony (1996), Saxony-Anhalt (1998), Schleswig-Holstein (2009) and Thuringia (1997). Three states, Berlin (1970), Hesse (1963–1974), and Rhineland-Palatinate (1975), have agreements with Catholic bishoprics. There have been three separate