Long-living legacy software systems grow old over time in tact with engineers retiring or changing jobs and technologies becoming obsolete even though they are still in use. Software archaeology helps new generations of engineers to understand such legacy systems to enable maintenance and modernization. Yet, the code base is large, hard to navigate and incomprehensible. The project ISA will exploit immersive 3D virtual reality to increase the effectiveness of software archaeology. We will create a virtual reality representation of a software system that can be explored interactively, for example, a city with buildings, floors and streets representing modules, functions and dependencies. We will analyze system usage to guide through meaningful exploration routes and highlight particularly important system areas as targets. The project will be conducted by internationally recognized researchers from the ITU Copenhagen in collaboration with a world-leading Swiss visualization expert, a high-tech German startup and two Danish virtual reality companies. The project results have the potential to substantially advance practices in software archaeology and make the field more accessible to classically trained software engineers, which is fundamental for coping with a dramatically increased number of legacy systems in the future.