Underground Kingdom “Mikawa Mu Valley”

Fun for all the family! A puzzle-solving adventure in an underground space

The former site of a tungsten mine was transformed into a mysterious underground kingdom to make this puzzle-solving adventure theme park. The underground space extends to around 1km in length.
As you step towards a world of darkness, guided by lights, the world of the ancient Inca and the legendary lost continent of Mu unfurls around you. Visitors are faced with statues of warriors and corridors covered with murals, and the plentiful sights that appear include an underground lake that emits a mysterious light. Travel back in time to a world of romance and imagination!
In addition to exploring the underground, there is also a gold-panning corner, a barbecue house, a restaurant, a center house, and other facilities to be enjoyed by all the family.



1564-1 Mikawamachi Nekasa, Iwakuni City, Yamaguchi Prefecture

Open Hours

10:00~16:00 (10:00~17:00 during peak season)

Closed Day(s)

Tuesdays & Wednesdays (excludes national holidays)
*Open every days during Spring vacation, Golden Week, Summer vacation, and Winter vacation


Not required

Time Required

60~90 min


Not available


Disembark at Nekasa Station on the Nishikigawa Seiryu Line, and take Iwakuni Seikatsu Kotsu Bus for around 7 min, then disembark at “Mikawa Mu Valley Bus Stop”. Immediate access on foot.


Adults: 1,980 yen,
Children aged 4~12: 990 yen, Children 3 and under: Free

Discount Tickets

200 yen discount when you show your Nishikigawa Railway Tokotoko Train ticket at the entry gate

Website (Includes Japanese language-only sites)