Increasingly powerful, handheld, networked devices provide an opportunity for educators to explore and implement ubiquitous learning (u-learning) environments through the extension of e-learning environments to include applications and services delivered to mobile devices. U-learning environments should be developed with both an understanding of human learning in general, and the learning of formally structured knowledge through de-structured u-learning environments. This study proposes a learning model for u-learning environments and a system architecture based on this model. The study outlines the features of the Walkabout u-Learning Environment, which has been implemented and trialled in accordance with the proposed model and architecture.