A digital twin offers various features such as visualizations, simulations with real data, and performance monitoring. Several of these features or parts of them can be implemented employing existing systems storing product data. However, to create a digital twin, these data being scattered to different systems is needed to be merged. For merging data and straightforward linking of these systems, this paper proposes a Data Link. The Data Link offers a single interface to access the systems via an API (Application Programming Interface) gateway and makes all data of the physical product available and accessible. In addition, it stores metadata about the systems and offers a user interface that allows searching the system that contains the required piece of information or implements the needed feature. The Data Link was implemented for an industrial overhead crane bringing operational data, control, and CAD (computer-aided design) models behind a single interface. The example implementation indicated that the Data Link based architecture for digital twins allows easy implementation of digital twins by using existing systems.