The brain codes continuous spatial, temporal, and sensory changes in daily experience. Recent studies suggest that the brain also tracks experience as segmented subdivisions (events), but the neural basis for the encoding of events remains unclear. We designed a maze for mice composed of 4 materially indistinguishable lap events, and report hippocampal CA1 neurons whose activity is modulated by lap number. This lap-specific ‘chunk code’ is separate from the spatial code. The chunk code remains lap-specific even when the maze length is unpredictably altered within the laps, showing that this code treats segmented lap events as abstract and fundamental units of the experience. The chunk code is reused to represent lap events when the maze geometry is altered from a square to a circle, suggesting that this code promotes a transfer of abstract knowledge between similar experiences. The chunk code tracks events and may be a fundamental representation of experience.