Memory is at the heart of our personality: the myriad of snapshots of our daily experiences have a pervasive and enduring influence on the self. But how is the multitude of individual memories organized in the brain? Our overarching model posits that memories are not stored in isolation but are rather represented in highly dynamic, hierarchical mnemonic networks. We investigate how fundamental principles of place and grid-cell coding (e.g., spatial mapping and remapping, modular and layer-specific organisation) relate to spatial cognition in humans but crucially also to the representation of information outside the spatial domain, such as mnemonic space. To unravel the underlying neural mechanisms, we pursue an approach that combines neuroimaging with life-like, realistic virtual reality tasks in humans. We are developing techniques for the rapid readout of representational space to provide a mechanistic understanding of human memory but also to develop biomarkers to identify its breakdown in normal and pathological ageing. Understanding the representational structure of our network of memories could open up the possibility to map how the brain assembles our rich inventory of knowledge