Central World

The Foundation World (基軸世界) is the universe in which the That Time I Got Reincarnated as a Slime series primarily takes place.

Background
The original universe created by Star-King Dragon Veldanava. It's a world of "chaos" that has the mixed properties of both a spiritual world and a physical world. It serves as the basis for all other "worlds", and its location at the "center" makes it especially easy for people and objects from other universes to find themselves there (especially the 'Demon Realm' and 'Spirit Realm' which directly "border" it) but inversely extremely difficult to escape.

Magic Continent
The Magic Continent (魔大陸) is the central continent where most of the series events take place. On the far west, there are the "Barren Lands", a great expanse of inhospitable sandy desert contamined with magicule radiations and the territory of Demon Lord Dagruel, on its border lies the Holy Empire Ruberios, a rich land and the territory of Demon Lord Luminous Valentine as well as the home of the Western Holy Church.

In the center of the continent lies a great collection of countries collectively referred to as the 'Western Nations', as well as the Jura Forest which contains the Jura Tempest Federation and is the abode of Storm Dragon Veldora. Both are considered the territory of Demon Lord Rimuru, although he's only publicly the ruler of the Tempest Federation. There's also the 'Canaat Mountain Range' to the north, a great expanse of mountains ruled on the surface by the Dragon Lord(s) who reside in the 'Dragon Roost' at the peak of the tallest mountain, and ruled underground by the Armed Nation of Dwargon. And at the southern border of Jura Forest is the Sorcerer's Dynasty Sarion, a collection of 13 elven states that swear allegiance to their divine emperor Elmesia El-Ru Sarion, but otherwise act independently to each other. Its "capital" is the state of El-Ru where the emperor and his family reside.

In the eastern border of the Jura Forest lies a collection of demi-human and majin populated states collectively the territory of Demon Lord Milim Nava. Its 'Capital' is the unnamed city currently under construction at the site of the former capital of the Beast Kingdom Eurazania. And finally to the far east lies the Nasca Namrium Ulmeria United Eastern Empire or more simply 'Eastern Empire', an expansionist empire made up of over 100 cities with a population of over eight-hundred million people. In the empire, people of all races are accepted without prejudice as long as they submit themselves to the emperor and anybody can obtain political power by joining the military. It is a land of "might makes right", ruled by its eternal emperor Rudra Nam Ul Nasca. Its capital is called 'Nasca' and is located next to a great holy mountain said to house the empire's guardian deity, Scorch Dragon Velgrynd.

Ice Continent
The Ice Continent (氷土の大陸) is the northern continent as well as the domain of the first Demon Lord, Guy Crimson. Its surface is constantly under a thick layer of permafrost and harsh weather due to the Frost Dragon Velzard's Aura, making it inhospitable to all but the strongest of living beings. The only known "settlement" is the Palace of White Ice, where Guy and Velzard, as well as a massive army of demons under the leadership of Rain and Misery, call home.

El Dorado
El Dorado (黄金郷 エル・ドラード) is the southwest continent singlehandedly ruled by Demon Lord Leon Cromwell. It has a large and active supermassive volcano at its center that constantly spews out ash and draws out large mineral deposits from deep under the surface, including gold, the source of El Dorado's income. It was also home to a "Hell Gate", which was managed by the Primordial Yellow.

Regions / Key Locations
Note: Other Key Locations are kept on the page of the continent.

Ocean
Not much is known about the ocean or what resides in it besides the Spear Toro and 'awakened demon lord level' monsters.

Information to be added.

Golden City of El Dorado
A city which resides besides a Volcano on the Continent of El Dorado.

Trivia

 * Teenage otherworlders despise this world since it doesn't have the pop culture and technology of Earth. Children are less inclined to this; they are too young to be absorbed in such things.

Information to be added.