Reincarnation Mountain.
It has only two levels. The second level is the true Path of Reincarnation, which leads across the Underworld River. It is guarded by the Dwarf race, whose sole duty is to welcome the return of the Son of the Underworld and nothing else.
Ruan Lianyu destroyed Reincarnation Mountain—specifically its first level—causing the Path of Reincarnation to vanish. To open it again, unless the Dwarf race receives a special signal, no one can find it.
Chapter 1218