On the left of the view, that is Mt.Ebott, referring to the Monsters sealed for a long time underground by Humans.

And on the right, it's a mordern city, which refers to the Humans living above ground. Between the two races, a deep hatred was accumulated because of the war.

But now, with the DETERMINATION from Frisk and Asriel, the barrier was broken down and the Monsters could be back to the ground.

And the rising SUN means the two previously opposite races, Monsters and Humans will be friends on the ground again, for a better and brighter future. That's what Toby want to tell us: show MERCY to your enemies, for everyone's better life, rather than fighting, pain, death other things like those.

These are personal opinions, not the official settings. Thanks for reading it. Good night.