The underground city was a general term.
It was not an underground city in the literal sense, but in fact, it was more or less the same.
However, Kant looked at the fortress that looked like a castle in front of him and understood that this was the underground city.
There were many arrow towers and the city walls were wide and thick.
This underground city was built in the middle of the karst cave. It was opened up by the mountain. There were holes of all sizes or houses that were specially built in the entire mountain. It was indeed like a city. It could be lived in, but it could also be used to defend against enemies.
A large number of shimmering moss and shimmering mushrooms grew in all directions of the cave.
Even the city walls and arrow towers also had this type of shimmering vegetation.