And this is exactly what a good engine does: occlusion, automatic removing of content. A good scene management renders almost only visible polygons and tries to generate as less render batches as possible and tries to minimize the amount of state changes in the graphics card.

But it is not only the scene management of models. The management of textures, memory and the quality and optimization of shaders has to be taken into account to achieve good performance.

Because of this a huge scene (indoor or outdoor, depends on your project) can be a good scenario to explore the power of such a technology.