I built a line of Nether Portals in a row so that you could walk through them and when you reach the end you go to the Nether (as shown in attached image), And it appears that when you line up Nether Portals like this, the first few portal blocks are invisible, but are still there (and still teleport you to the Nether and can be broken in creative). Also, if you look through the other side, the third one down is rendered, showing up the same way as the front.
It might cause a bit of lag if they all were rendered, but I think that at least the first one should be visible.
By the way, The image I uploaded was not rotated 180 degrees, but is showing up like that on my computer.
Also, the image is in bad quality because I can't use this website on the computer I use Minecraft, and I also can't use mail, so I had to take a picture by hand and upload it on another computer.
Here is a row of portals, none of them render for me and the outline of the 'portal' block is rotated 90°.
I was teleported instantly when I touched the first portal, so a line of them may no longer be necessary.