Weird, as I can see those pictures in a correct size. Nevertheless, the text part should explain the bug well enough.
EDIT: The images are now as large as I can get them. And to explain the second screenshot, I have placed no blocks on ground. The rock thing that can (or should) be seen is the top of the tunnel placed underground.
Yeah, now the images are good, thanks!
Unfortunately you were using some mountains in the back.
If the tunnel blocks don't raise the ground, and don't cause texture glitches, then it should be still ok?
It does cause texture glitches. Hopefully the following picture shows it better. The strange rock thing in the middle of the road is a roof of a tunnel placed right under it.