In FireRed and LeafGreen, like Birth Island, Navel Rock is invisible on the Town Map by default, only appearing when the player first arrives there. This is in contrast to the other Sevii Islands, which do appear on the Town Map. In Emerald, it never appears in the PokéNav's map.
A Ho-Oh appears on 4F on the first visit. If defeated, it respawns after entering the Hall of Fame. If run from, it respawns upon leaving the area. Although it is encountered outside, at the top of Navel Rock, it is still considered to be a cave environment.