In the 60s, when I was a kid, I remember watching the pilot episode of the TV series: The Time Tunnel. What really impressed me was the huge scale of the time tunnel in the subterranean complex; then, over the next months until its abrupt cancellation, I was a little disappointed with the show given that those initial shots did not recur again.
One thing that never made sense to me was that the depth of the tunnel in the regular episodes looked very short if compared with the long side view of the tunnel in the first episode. Obviously, given that I was just a kid, I had no idea that the real world repairs in expenses when it comes to fictional recreations, thus, I wonder if someone has grasp details about the concept sketches of the Tic-Toc project with the tunnel models, etc. in any media (Leinster's novel, Allen's script, comics, DVD, games) where the length of the tunnel is specified.