Navigation is a complex cognitive ability requiring the processing and integration of several different types of information extracted from the environment. While navigating, however, an unexpected event may suddenly occur, which individuals are required to detect promptly in order to apply an appropriate behavioural response. The alerting mechanism that is integral to the detection of unexpected events is referred to as the bottom-up attentional system. Using event-related functional magnetic resonance imaging, we investigated the neural basis of bottom-up detection of unexpected events while individuals moved within a virtual environment. We identified activation within a right fronto-temporo-parietal network in response to unexpected events while navigating in this virtual environment. Furthermore, when an unexpected event requires an adjusted behavioural response, a region of the right ventrolateral pre-frontal cortex (areas 45 and 47/12) is selectively activated. Our data replicate earlier findings on the neural mechanisms underlying visual attention and extend these findings to the more complex real-life ability of spatial navigation, thereby suggesting that these neural mechanisms subserve the bottom-up attentional systems that are crucial for effective locomotion in real surroundings.