Walter Christaller was a German geographer best known for developing the Central Place Theory in the 1930s. This theory explains how cities and towns are organized in a hierarchical manner, with larger urban centers providing services to smaller surrounding areas. His work aimed to understand the spatial distribution of settlements and their economic functions. Christaller's theory is based on the idea that people will travel certain distances to access goods and services, leading to a pattern of central places that serve as hubs for trade and commerce. His research has influenced urban planning and geography, impacting how cities are designed and developed.