like make a door in the midst of a room that lets the player see through another dimension and walk through it?
I will be starting a project about a dream like world (inner world) and i need to know if this is possible and how i can do this
ty for taking your time 
Yes, it is possible.
Take a look at these videos, that’s where I would start
wrapzones, portal in unity free and for the second video here is the
project.zip you can open it and see how it works, for more info go to algoholic.eu.
You could render other cameras to mesh surfaces with render to texture which is for pro only, but there is a workaround to achieve the same thing in Unity Free. Good luck!
Radivarig