Primordial Forest
As the name implies, it's a 'forest' that has been preserved in its original state without any alterations.
However, the forest here is unlike any that humans would define,
during the earliest construction phase of the Cancer Palace, among the cancerous cells responsible mainly for 'architectural proliferation,' one cell underwent a peculiar mutation. The structures it proliferated were no longer pre-set frames of buildings or piping systems, etc.,
but rather trees and plants made of flesh.
When the chief engineer prepared to exterminate it, the Lord ordered its preservation and even specifically designated an area within the Cancer Palace for its unchecked growth.
Ultimately, there formed a forest of fleshy trees purely comprised of cancerous cells,