Recent developments in mobile and wireless communication technologies have played a vital role in building the u-learning environment that now combines both real-world and digital learning resources. However, learners still require assistance to control real objects and manage the abundance of available materials; otherwise, their mental workload could become so high that learning becomes less effective. The learner is the priority in every learning situation and is, therefore, a crucial factor in executing u-learning. This study presents a u-learning system that integrates context awareness and ontological technology to design a context-aware knowledge map (CAKM) to improve learning efficiency. A case study of an Orchid Island botanical ecosystem course was conducted in classrooms and at the Botanical Garden of National Museum of Natural Science in Taiwan. Participants were university teachers and students. A questionnaire based on the technology acceptance model (TAM) theory was designed and used to measure the willingness for adoption or usage of the proposed system. The results demonstrate that this innovative approach can enhance learning intention. The results also indicate that this CAKM not only substantially improves the effectiveness of subject learning but also enhances the usability of u-learning systems in the museum environment.