Location-based games have the power to transform specific environments into thematic learning experiences. However, their learning content is often managed only by developers and users cannot create their own content, or customize existing ones. This issue affects specific related actors, like teachers, who cannot make use of these technologies to create gaming scenarios for their own purposes. This paper introduces SmartZoos, a location-based game, designed to enhance visitors experience in Zoos. Through it, we present a design mechanism that allows users to generate location-based learning content, as modular Open Educational Resources. These modular contents can be later integrated independently into multiple gaming scenarios by other users. Preliminary results conducted as part of an iterative co-design process, reveal that the prototype is being perceived as effective and easy to use.