Altering Cave can be found within Outcast Island on Six Island of the Sevii Islands. Back when Pokemon FireRed was first created, Altering Cave was to serve as a location to collect data from Wonder Spots (which would've seen the Wild Pokemon found within the cave to alternate at different times). Unfortunately, this never came to be outside for those living in Japan back in the day, effectively making Altering Cave completely empty and thus useless. The Pokemon that were to alternate within Altering Cave were suppose to be Zubat, Mareep, Pineco, Houndour, Teddiursa, Aipom, Shuckle, Stantler, and Smeargle.