The imaginative journey is one through which the traveller is taken into their own world of imagination, filled with speculation or inspiration, most commonly in the form of dreams.
the first imaginative journey (a small one) in the beginning is when dorothy is singing the classic song - "somewhere over the rainbow"... here, shes dreaming of the "place over the rainbow" (which she ends up going to when up in the cyclone)
ok pretty much the whole movie is an imaginative journey from the point when dorothy arrives home to find a cyclone has struck her town...
when inside the house (which has been lifted up inside the cyclone), she is dreaming
she sees people passing by her bedroom window - note: the "wicked witch of the west" or that other lady..ms gulch i think - she tries to take away toto
anyways yeh when the cyclone appears to be over.. dorothy and toto step outside of the house and realise "they arent in kansas anymore". notice the colours in this part of the movie compared to the beginning - prior to the she steps outside of the house, we've seen the movie in black / white or it mite be brown/white... anyways yea... then when u look at the world dorothy is in after she steps outside u see its full of colour and nature (compared to the brown/dullness of reality - the harsh life on a kansas farm)
the colours and nature perhaps represents the bright youth of dorothy's mind (as she is dreaming of the place "over the rainbow" as sung previously)...
ummm then u can go on and on about the imaginative characters such as the munchkins, the friends she makes along her imaginative journey "down the yellow brick road" [tinman. lion and scarecrow], the supernatural encounters she meets - the magic of wizards and witches... and how in the end dorothy has the power to return back to kansas with toto just by "tapping your [her] shoes three times and saying theres no place like home"
hope it helps.. mite have missed some stuff .. too early in the morning for me.. haha