The power plant that used to draw energy from the lava of the volcano is gone. All the Pressure Plant buildings have just been covered by a gigantic bright yellow trapdoor radically changing its landscape.
And that is not all. According to the fortrisen account, the trapdoor would be opened to reveal a new place under the volcano.
We can see that the space under the hatch is divided into three levels: B1, B2, and B3. We can imagine that these are intended to open one after the other as the weeks go by. It is impossible for the moment to know what is hidden in this basement as nothing is clearly visible in the images above.