A location-based service is provided that allows a user of a mobile device to tag and track the places he or she visits and share these places with social networking members. To implement this service a system receives location information from the user's location-aware mobile device over a wireless network. The location information identifies various locations or other points-of-interest that the user has visited. Based on this information the system determines a geographical domain that encompasses at least some of the locations the user has visited. Once a geographic domain has been determined it is presented to the user via the mobile device. The user is prompted to tag the geographical domain with an annotation that describes the geographic domain. The system stores the geographical domain and the annotation associated therewith so that it can be searched and accessed or retrieved by the user or members of the user's social network.