Augmented Reality (AR) is a technology that can be used to provide personalized and contextualized information regarding physical objects in form of digital overlays. We use this technology in our research project Ambient Learning Spaces (ALS) to provide museum visitors with specific additional digital 3D information regarding the exhibits presented. With this technology, we enable museum curators to use a new form of transporting contextualized information without the need for additional physical space. However, the use of AR brings up new challenges for the creation and placement of digital contents into the museum space. In this context, we ran an anonymous survey on the use of AR in museums throughout Germany and studied responses of (N = 133) museum professionals. The results indicate that, although many museum professionals are interested in using AR technology, currently the integration is very costly and complex. This paper proposes a system we developed in a user-centered design process with a museum. This system provides an interface that helps museum professionals to cope with the complexity when placing and aligning digital 3D objects in their exhibition using mobile devices. Through this solution, visitors have the chance to experience the virtual objects spatially embedded in the exhibition by the curators themselves. In multiple user studies during the development phase we measured the usability of the interface. The findings show that the system provides a high degree of usability and can be applied effectively by museum professionals.