The hippocampus plays important roles in learning and memory. In the hippocampus, spatial information is encoded by place cells during an experience and consolidation of spatial memory is supported by reactivation of place cells during rest/sleep periods. It remains to be unknown how multiple spatial experiences that are encoded by a subset of place cell ensembles are reactivated in subsequent rest/sleep periods. To address this issue, we recorded spike patterns of hippocampal CA1 and CA3 place cells in rats that sequentially experienced five different rooms. We confirmed that CA1 cells had larger numbers of place fields defined from individual rooms that CA3 cells, suggesting sparser spatial representations by CA3 cells. Overall, increases in reactivation rates of CA1 place cells from pre-rest to post-rest periods were correlated with the numbers of place fields, suggesting stronger reactivation in neurons that encoded more information during awake periods. We now analyze synchronous spike patterns of multiple neurons to clarify how experiencing multiple environments are encoded and consolidated by hippocampal neuronal ensembles.