Jiang Yan had just returned to the shelter when Qin Lang and Ye Qing also happened to come back.
They were holding some water and dried food in their hands, along with a first-aid kit marked with a red cross and three paper maps in waterproof bags.
The maps were spread out, showing a dense network of lines, like a combination of a beehive and a labyrinth.
The starting point was Flame Base, the destination Yaoben Base.
The main tunnel for the operation of the train had the widest lines, marked in red.
Beyond Yaoben Base, there were a few short red lines leading to unknown locations, unmarked.
Jiang Yan glanced at it and couldn't help but marvel inwardly.
The construction project must have consumed a lot of special metallic materials; it would have been extremely difficult to build, fire-resistant, waterproof, ventilated, and with the highest level of earthquake resistance—the cost must have been astronomical.