Not the only reason

As mentioned before, the entire Upside Down World was only 1341 kilometers long. Considering that Himatikia was above the Transition Realm and could fly, it obviously didn't take long for them to arrive at the purging organization's headquarters. 

Celis and the twins looked far ahead and noticed that the area around them was increasing in size. So far, this tube-like world was only twenty kilometers in diameter if one moved sideways until one reached the same point again. However, the twins could tell by looking around that it had already increased to at least twenty-five, not to mention that it was getting bigger the farther they went.

Suddenly, Celis and the twins noticed something that looked like a giant tower in the distance. By far, that was the biggest building they saw in this Upside Down World. However, it wasn't its size that really caught their attention. Instead, it was the fact that it looked to be completely white. "Isn't that the white powder?"