Walter Christaller (1893 – 1969), was a German geographer whose principal contribution to the discipline is Central Place Theory , first published in 1933. This groundbreaking theory was the foundation of the study of cities as systems of cities, rather than simple hierarchies or single entities.
Before 1914, Christaller began studies in philosophy and political economics and subsequently served in the army; later, during the twenties, he pursued a variety of occupations. In 1929 he resumed graduate studies that led to his famous dissertation on Central Place Theory in 1933.
At the end of the 1930s he held a short-lived academic appointment, but then joined the Nazi Party in 1940. He moved into government service, in Himmler's SS-Planning and Soil Office, during the Second World War. Christaller’s task was to draw up plans for reconfiguring the economic geography of Germany's eastern conquests ("General plan of the East") – primarily Czechoslovakia and Poland, and if successful, Russia itself. Christaller was given special charge of planning occupied Poland, and he did so using his central place theory as an explicit guide. 
After the War he joined the Communist Party and became politically active. In addition, he devoted himself to the geography of tourism. From 1950 forward, his Central Place Theory was used to restructure municipal relationships and boundaries in the Federal Republic of Germany and the system is still in place today.
- Christaller, Walter (1933): Die zentralen Orte in Süddeutschland. Gustav Fischer, Jena.
- Rössler, Marc (1989): Applied geography and area research in Nazi society: central place theory and planning, 1933-1945. Environment and Planning D: Society and Space 7, 419-431.