Topographic organization characterizes hippocampal circuits, yet its functional significance remains unclear. By selectively disrupting CA1-to-subiculum topographic projections in latrophilin-2 conditional knockout mice, we show that precise topography shapes the anatomical distribution of subicular spatial coding while preserving single-cell tuning. Disrupted topography also selectively impairs boundary vector coding and long-term network stability. Thus, CA1 inputs provide an indispensable scaffold for organizing subicular spatial maps and dynamics.