Various mobile augmented reality applications have been developed for cultural heritage sites especially in Europe. However, these existing applications focus on the application content without concerning on the enjoyable and informal learning concepts. This study found that enjoyable aspect and informal learning concept are necessary to promote learning processes at cultural heritage sites. Therefore, this study proposes a conceptual model of mobile augmented reality for cultural heritage site towards enjoyable informal learning. In the proposed model, user requirements were collected and determined through a field study of enjoyable informal learning content at cultural heritage site. This paper presents the results of the field study which detail out the conceptual model with three structures, ten elements, and thirty seven supporting elements. The conceptual model could benefit to the designer of mobile AR to develop such application by implementing various elements to cater enjoyable informal learning experience.