This castle was virtually identical to the the one constructed by Arthur during the Saito extraction job. Unlike Arthur's castle, the limbo version is filled with heavily armed Japanese guards instead of partygoers and suited security guards in the interior.
The Japanese castle seen in limbo is set during the day, unlike its counterpart constructed by Arthur.
The castle was just above the shore of a large beach and was seemingly populated by Saitos projections of Japanese guards that served as his "sub-security". Saito himself was seen in a large dining chamber, where the guards brought Dominick Cobb, his totem and a gun, after he washed up on the shore. It is here Saito remembered that limbo was not his reality and Cobb convinced him to "Come back, so [they] [could] be young men together again." Saito and Cobb then presumably killed themselves with the gun, and the two woke up on the flight to Los Angeles with Robert Fischer and the rest of the team.