mutli set switching, please help

[dwaik]

hello i have a palace with two sets, interior and exterior, i want to do a walkthrough, firstly i want to display the exterior set, and when the camera enters the palace i want to display the interior set, my question is : whats the best way to do this, shall i use visibility control or load/unload? and how to apply i mean when to switch between these two sets?
thank you in advance