From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
The Yama Realm (閻魔界, Enmakai) is a gateway between the physical plane of existence and the Next World. It serves as both Yama's palace and his office, where he passes judgement over dead souls by sending the good ones to Heaven and the bad ones to Hell.
In this mansion, Yama is helped by other Ogres. Under certain circumstances, Yama had allowed certain deceased individuals to retain their bodies, usually those who had done heroic deeds, e.g. Olibu, Son Goku, Paikuhan, or who had high power levels. Yama Realm was also adjacent to the Serpentine Road, Hell, and a punishment room that Yama claimed to have sent Raditz when he resisted Yama.
The Yama Realm made its first appearance when Goku died and was sent to the Next World after his battle against his older brother, Raditz. From here, Goku was able to travel the Serpentine Road] to be trained under North Kaio in preparation for the Saiyan attack back on Earth.
In Dragon Ball Z: Fusion Reborn, Yama Realm now had three floors. The film also depicted the gateway between Hell and Yama Realm having a purification device which cleansed souls of excess evil energy. It was an overflow of this energy exploding on a young Ogre that caused the creation of the monster Janemba, who proceeded to cover Yama's Palace in a thick piece of blob, which could only be broken when yelled at and given hurtful insults.
The Yama Realm appeared in cutscenes in various video games, such as Dragon Ball Z: The Legacy of Goku, Dragon Ball Z: Budokai, and Dragon Ball Z: Harukanaru Densetsu. It is a location in the Next World in Dragon Ball Z: Buu's Fury and Dragon Ball Z: Attack of the Saiyans. Notably, in Buu's Fury, Goku and Vegeta are summoned here by Yama after the Yama Realm was attacked by Janemba.
The palace is a battle stage in Super Dragon Ball Z where it is named King Yemma's Palace.
- The entrance to Yama's Palace has the words 'WELCOME' on it with a space between the 'L' and the 'C', making it look like 'WEL COME'. The first time this was ever seen, the letter 'L' was shown twice without the space and it spelled 'WELLCOME'.