With global climate change and the progressing digitization of infrastructural projects, the BIM (Building Information Modeling)-method has become increasingly significant. For planning and managing BIM projects, GIS data is crucial, e.g., in the form of environmental data. Especially for large-scale infrastructure projects, integrating BIM models and GIS (Geographic Information System) data provides advantages. With an information-rich platform that aggregates geographic and infrastructural design information to provide geometric 3D visualization combined with semantic information, processing infrastructural projects can be simplified. Many integrated solutions require complex algorithms and additional manual work for converting and visualizing BIM models. This process potentially leads to the loss of model information or contradictory data. In addition, commercial software is required. We present a new approach for the BIM-GIS integration based on open-source frameworks. Various types of BIM and GIS files can be uploaded to the application. The files are unified in one 3D environment with absolute reference, for which the coordinate reference system of each file is temporarily converted to a user-definable coordinate reference system within the backend. The original files remain unchanged, so the application serves as a viewer and allows the user to view all geographical and infrastructural information. Furthermore, various tasks like coordinate transformation and geometric measurement can be performed. Besides the viewer functionality, the application enables users to annotate the data and provide feedback on the issues found in the BIM models. That allows various stakeholders to share their insights, which is crucial for managing infrastructural projects and seamlessly displaying BIM models and GIS data.