An online system uses a model to determine affinities of users for geographical locations. Using the affinities, which may indicate travel-related preferences of the users, the online system may customize content items to include content captured by client devices of other users of the online system. For example, the online system presents to a particular user a content item including a photo or video of a geographical location captured by a camera of a client device of another user who is connected to the particular user. The model may implement, for example, collaborative filtering or other machine learning techniques to determine commonalities between users' travel affinities. Additionally, the model may determine latent properties or temporal trends of user preferences based on training data including historical actions performed on the online system or social data. The model may also classify different types of geographical locations.