In this contribution, we present the architecture and implementation of an Augmented Reality (AR) system that enables museum professionals to create and edit AR tours inside their exhibitions without programming knowledge. Museum professionals can use content created during their regular digitization projects and transform them into rich AR content. To create and edit AR tours a web-based frontend called the Ambient Learning Spaces (ALS) Portal has been developed. The media and metadata are stored in a semantic database inside the Network Environment for Multimedia Objects (NEMO) backend and middleware system. To present the tours to the visitors, the platform-independent mobile AR app InfoGrid has been implemented. The content of AR tours can consist of text, audio, video, and 3D objects. Additionally, we added the option to use the new dynamic overlay type Asset Collection as an AR element. This allows the museum staff to dynamically add animated interactive 2D/3D objects into the AR tour at runtime. The system has been applied and evaluated in the context of a natural history museum.