Human cerebral cortex contains an uncertain number of structurally segregated regions interconnected by a dense network of axonal pathways. Using DSI, we map these pathways in individual human subjects. An analysis of the resulting large-scale structural brain networks reveals the existence of a core within the brain, as well as several distinct clusters. Regions within the structural core share high centrality and they form connector hubs that link all major modules of cortex. Most key regions of the human default network are also members of the structural core indicating an important role of the core in shaping functional integration.