I for one would have liked to see the surroundings about this portal, as it is not very interesting as it is right now. Also I believe this shot would improve if you had used a polarizer to make the sky more dramatic and there is a small dust spot almost in the dead center of the frame. In short I like this shot but due to all the reasons I just named it´s only an average shot in this challenge for me, 5 from me.
This is both well shot and an interesting composition, sort of a "doorway to infinity" kind of thing... Well done! Only criticism; I might have cropped it a bit, taking some off the bottom.