Location from Undertale / Deltarune by Toby Fox
A bioluminescent cavern of echo flowers, ancient history, and the sound of running water — the Underground's most beautiful and most mysterious region.
Waterfall is where Undertale gets quiet and strange. The Echo Flowers whisper old conversations. The gems on the ceiling look like stars to monsters who have never seen the real sky. The Wishing Room is full of wishes from monsters who want to see the surface. Ancient glyphs on the walls tell the story of the Human-Monster War. Undyne patrols here. Napstablook lives here. The path through Waterfall is haunted by beauty and sadness in equal measure. This is where the game reveals its lore — the war, the Barrier, the prophecy of the Delta Rune. The ambient storytelling is extraordinary.
Indigo and blue caverns with glowing mushrooms, luminescent gems on the ceiling that look like stars, and water everywhere — pools, streams, waterfalls that give the area its name. Echo Flowers repeat whatever was last said near them, creating a landscape of whispered memories. The light is always blue. Everything glistens.