They often pierced the hills with tunnels and bridged the valleys or swamps.
The length of tunnels varies greatly; the longest are about a mile.
He knew he would find only chill emptiness ahead of him in the tunnels.
We were taken down one of these tunnels, and into a still larger one.
"Ask him if there are any tunnels between the ship and the river," I commanded.
The walls were so thick that the windows looked like they were set at the end of tunnels.
In winter he is quite as active as in summer and tunnels about under the snow.
That is because his tunnels are found running along the rows of plants.
So mountainous is the land that it would have to be one series of tunnels.
They have workers, who bore the tunnels and build the mounds.