Infierno-moler (lit, Hell Grind) is a massive stone mountain in Hueco Mundo. It is made of a blackish mineral, and is large enough to be viewable from Las Noches. It is also very steep and impossible to climb, making it an ideal location for the arrancar, Lucia's, lair, since their sonido can carry them there. It is bare of life, except for a single blue flower marking the entrance to her lair. There is a section of Infierno-moler that looks like it is solid rock, but you can pass right through it and enter the arrancar lair.