The proximodistal axis is considered a major organizational principle of the hippocampus. The CA2 region apparently breaks this rule. We discovered that CA2 is organized around the limit of the mossy fibers (Fernandez-Lamo et al., Cell Reports 2019). We found a characteristic molecular gradient within CA2 and marked trends of oscillatory firing.  Our data suggest that the structure and function of CA2 are distributed along the proximodistal hippocampal axis.