Within the dark underground tunnel, a perfect silence prevailed.
Originally, there weren't any routes in the Underground world. Only irregular rock fractures and water channels formed after thousands of years of water erosion. However, through the endless excavating efforts by many generations of underground creatures, the winding cave system with many chambers, large and small were interconnected by tunnels of all length, forming an awe-inspiring three-dimensional tunnel system that extended in all directions.
There weren't any straight paths down here, like the ones back on the on the surface. All the passages were meticulously excavated along rock fractures. Stretching through those ancient water channels, twisting and turning. Sometimes, when the walls between caves were relatively thin, you could hear sound from other passages, but they were still forced to travel a long, winding passage of tens of miles in complete darkness, before reaching their destination.
