Although the underground drainage was just an additional construction that the Officials installed to compensate for the underground air-raid shelters, they put quite some effort into it during construction, incorporating many ingenious designs inside.
And most crucially, compared to completely independent underground air-raid shelters, the underground drainage system, with its interconnected network of pipes, could facilitate immediate evacuation from problem areas when necessary.
Since there was nothing interesting to see in the underground drainage, Zachary merely took a brief tour and was ready to return.
Just as Zachary approached the staircase, he found his father and mother just coming out of it, exchanged a few simple words with them, and was ready to go back upstairs, not wanting to disturb his parents' subsequent visit.
When Zachary was about to go upstairs, Mr. Thompson suddenly seemed to remember something and asked him, "Son, have you been to the room across? "
