Christaller's Central Place Theory and Reilly's Law of Retail Gravitation describe models for how settlements are arranged and influence each other. Christaller's theory proposes that settlements will be arranged in a hexagonal pattern with higher-order settlements further apart and providing services with a higher threshold and range. Reilly's law uses gravitational models to determine breaking points where customers are equally drawn to two settlements based on their populations and distance. However, both models rely on unrealistic assumptions and do not perfectly predict human behavior or reflect real-world conditions. While not fully realistic, the theories can still provide some guidance for planning.