Then he reached up and excavated a hole in the top, forming a vertical tunnel.

They crowded into the vertical tunnel and dropped down to the dark green air lock.

Now they were in a vertical tunnel, still dropping.

He stood on tiptoe, reached up into the vertical tunnel.

She began at once to dig a vertical tunnel in the sandy clay soil.

Isn't that what you call those vertical tunnels of open water?

They were in what appeared to be a long, vertical tunnel.

It has a vertical tunnel in the middle for two plants.

It felt like she was in a vertical tunnel, or perhaps a narrow tower.

Lee and Thomas step past him, climbing lower into vertical tunnels ahead.