Thank you. I have an idea how to make it another way:
I'll make two rooms (in one level), each of rooms has a door, how can I move from one room into another an back via doors (smoothly so I could be even able to stop right in the middle of the doorway and turn around, move etc (as in portals in Portal game))? I know that I can use views to see the next room in the doorway. But I have no idea how to handle smooth moving between levels?