In most visual depictions of the Mahabharata and the Gita, Lord Krishna is shown as though expanding in size and form, until he becomes humongous. So large, that he opens his mouth, and many galaxies are seen inside it. He has myriad arms and legs and heads, and in general is representative of a supernatural being.
But this may not be fully accurate. Because the Lord in his own admission, states that everything is He, and He is everything. So all the empty space around us, all the filled space around us, all the objects, all the living creatures – everything is Him only.
And thus the Lord’s viswaroopa is to be seen as a wake up image for Arjuna (and by extension us). The whole of the 10th chapter where Krishna gives so many examples of his manifestations in the world around us (vibhutis) was not enough to convince Arjuna.
But when he did finally see the True form, not only was he amazed, but also terrified. Why?
Because he saw Krishna as the Creator, but did not expect to see his Destroyer side (all of creation was eventually being destroyed). He had forgotten the lessons he learned in chapter 2 on aham or ego. He was unable to reconcile his friend Krishna, as also the terrible Krishna. But as the Lord himself says, all this is a play of maya. As my Guru says, “Once we are out of ‘body consciousness’, all these will be taken care of”.