Ferrum Grotto was a cave system that housed several Force-imbued crystals. The grotto was located on Gymbol near one of its few bodies of water, Lake Vida. The planet was a major source for lightsaber crystals for Jedi. The cave epicenter was the location that stored the largest crystals that contained the most apparent Force and lightsaber-beneficial qualities to them. The epicenter was also home to the widest array of colors throughout the entire cave system. Reports of Force-induced visions made the cave a sacred place for Jedi. The various pilgrimages to the site created a light side nexus in the cave.
The epicenter was the most difficult portion of the grotto to get to because of its positioning above the peripheral portions of the cave and the density of the crystals surrounding the epicenter at its peak. Flooding from Lake Vida also made the cave inaccessible at times.