Tunnel Vision
They did not prepare him for this. The tunnel was a mile long, maybe longer. The walls were solid enough, but he noticed a black oil-like substance coating the surface. Luckily, the same grease-slime was not on the walking path. In fact, the trail that snaked down the tunnel appeared firm enough to support him.
He stood up and balanced some of his 250-pound body weight on his right foot. Feels fine. Now the left foot. So far, so good. He was sure he had broken an ankle when he fell, but apparently not. Once he discovered he was unhurt and able to walk, he began to move down the pathway. One step, slowly, then another. The walking surface was strangley comfortable, like walking on a well-sodded lawn. He took time to look around him.
The tunnel was about fifty feet wide, he guessed. The ceiling above was high. Light was available to lead the way, but from what source he could not tell. There were no lamps, no fires, no lightbulbs. He was thankful for the light, but afraid of being alone.