I have been to Kumano Kodo, which is the “Sacred Sites and Pilgrimage Routes in the Kii Mountain Range”.
It has been registered collectively as a UNESCO World Heritage Site.
Such a meditative place around the old trail!
This World Heritage site consists of three sacred locations-“Kumano Sanzan”, “Yoshino & Omine” and “Koyasan”-
and three pilgrimage routes linking the sites-“Kumano Sankeimichi (Kumano Kodo)”, “Omine Okugake-michi” and “Koyasan Choishi-michi”.
This is Kumano Hongu Shrine located in the middle of Kii mountain range.
Though taking about half day from Osaka, you will have a gorgeous train trip to the area if you hold a JR pass with Ocean-viewing through the window going along the coast of Ocean Pacific.
Please ask the staff if you are interested in it. There are also nice outdoor hot springs.