Besides creating some realistic images from 3d models, a new type of visualization is emerging as the future of architectural visualization. A few years ago interactive visualization of architecture was only created by studios or artists looking to prove their technical skills, or fulfill the request of a particular client. Even the consumer level technology related to the production of interactive 3d was in the early stages of development. It was either too expensive of difficult to produce interactive 3d for architecture.
For a long time, Blender is an easy, fast and affordable way to create interactive 3d for architecture. By using the Blender Game Engine, you can even get some of the stunning visuals created by Cycles and bake that in textures to use in interactive 3d.
If you use the Blender Game Engine for architecture, there are a pack several types of doors ready for use in BlendSwap. The artist responsible for this impressive pack has an alias of RedFrost. All of the doors are available with a creative commons zero licenses. You will find all kinds of doors in the collection, and it may be useful not only to use directly on your project or as a learning resource since they have the game logic necessary for interactive architecture ready to use.
The news of a possible removal of the Blender Game Engine in the upcoming Blender 2.8 may discourage some people to invest in interactive architecture using Blender, but it is not confirmed yet.