Six classes of beings
Six classes of beings (wyl. rigs drug)
Localisation of the six realms according to the Abhidharma litterature
Most of hell beings and pretas live in the earth below the ground.
1-The Hot Hells are one under the other from the Reviving Hell down to The Hell of Unrelenting pain which is 20'000 yojanas below this world. Each is surrounded in the four direction by the four Neighbouring Hells one after the other. The Cold Hells are also below the ground one on top of the other in an other location. It is said that since the world is an immense gathering of particles, they can all fit. It is often considered that the Hot Hells are below Mount Meru while the Cold Hells are below Lake Manasarovar. According to the Mahayana though, since the Hell Realms are actually understood to be one's own perception, it is not necessary to consider them as a definitely existent.
2-Pretas live 500 yojanas below the earth.
Beings in the Ephemeral Hells and “pretas who move through space” do not inhabit fixed abodes. They can live below the earth, in the human realm, or other places.
3-Animals either inhabit the great oceans (“Animals living in the depths”), or live mostly on the earth, in water, in trees, in the realms of the gods or humans (“scattered animals”).
4-Demigods inhabit cavities inside Mount Meru down to the universal golden basis, some above water line, some below. The demi-gods living above the water line are sometimes counted as animals and include their chiefs such as Rahu.
6-As for the gods, There are six abodes of the gods of the Desire Realm. The gods in the Abode of the Thirty-three live at the top of Mount Meru. The gods in the Abode of the Four Great Kings reside on the four terraces at the top of Mount Meru just below the Abode of the Thirty-three, as well as on the crests of the Seven Mountain Ranges, in space and so on. In the sky above the Abode of the Thirty-three, are the four other abodes of the gods of the Desire Realm, one above the other.
Above these, are the Seventeen Heavens of the Form Realm.
Though the abodes of the Formless realm, being formless (in other word non-physical), have no separate location, they are also called "celestial worlds".