Thread-like structures that form the boundaries between large voids in the universe.
1
Meanwhile a great wall of sea advanced from the centre of turmoil.
2
I glanced behind me, and of course the great wall was gone.
3
Consider the great wall of China: ponder the great populace of Pekin.
4
But they discovered a breach in the great wall and passed through.
5
Litter from the great wall of trees had fallen on the rocks.