Through an endless tunnel
In my dream last night, in trying to escape from some unexplained capture in an empty building, I found a hole between two walls, and cautiously climbed in to explore. Inside, the walls of the tunnel were a light sandy colour, and though I climbed further and further, it did not grow dark. My exploration was stepwise; at every forking of the tunnel I chose either left or right, up or down, and the tunnel would bend and turn, made me dizzy, loosing my orientation, I had the feeling I was sometimes climbing the wall, sometimes the ceiling, and soon I lost track of how to retrace to the exit - and I panicked.
Illustration courtesy: Apple-pine.blogspot.com