From Discworld & Terry Pratchett Wiki
The Discworld is the setting of most of the books by Terry Pratchett. It is a magical world in the shape of a disc which - as in certain well-known ancient cosmologies - is mounted on top of four giant elephants which are standing on a giant turtle. Another (possibly better) description would be "like a geological pizza but without the anchovies". The Discworld universe operates through the effects of narrativium, which explains its fundamental properties.
The turtle's name is A'Tuin, more often known as the Great A'Tuin. At least, that is the name some people gave the large turtle. It is unknown what the turtle calls itself. The sex of the turtle is also unknown, but there are some scientists on the Disc who have devoted their whole lives to finding that out, called chelonauts. (it would be an important matter should the Star Turtle ever find a mate). It is possible that it is female, because of its interest in the eggs which hatched in The Light Fantastic.
Because of the world being a disc, the "usual" directions such as north or west do not apply and are unheard of. Instead the directions are hubwards (toward the center of the Disc), rimwards (toward the edge of the Disc), turnwise (along the direction of the Disc's spinning) and widdershins (counterturnwise). Terry himself has said about the Disc's cardinal directions that
There are four cardinal directions on the Discworld: hubwards, rimwards, turnwise and widdershins. Seasoned travellers have learnt to navigate solely by the sensations that they feel. If it gets warmer, you are headed rimwards. If it gets colder, you are headed hubwards. If you get dizzy, you are headed widdershins.
The Disc's full spin cycle takes 800 days, where each year contains two summers, two winters and so on (see also Discworld calendar).
The Disc: Physical Geography
The disc is about 10,000 miles across and about 30 miles thick at the Rim, but a lot thicker at the Hub. At the center of the disc a large mountain (Cori Celesti) reaches into the sky, whereas at the Rim a large amount of water continuously flows over it (Rimfall). How this status can be maintained without running out of water is unknown, but probably is also caused by the Narrativium. The Rim is partially surrounded by a fence called the Circumfence, keeping people and ships from dropping off the world. Major oceans are the Rim Ocean and the Turnwise Ocean. There are four major continents and some other islands and archipelagos, such as the Brown Islands.
The Moon that circles around the Discworld can only do its complete course if one of the elephants will occasionally lift a leg and let it pass beneath. It is the same for the Sun. The moon is slightly closer to the Disc than the sun, and is covered, on one half, with silvery glowing plants, which feed the lunar dragons and illuminate the sky - unlike on Roundworld where the moon needs surrogate light from the sun. The other half is burnt black by the sun. The moon rotates, and completes a full revolution in about a month; the full moon occurs when the luminescent side is completely visible from the Disc, the new moon when the dark side is shown.
The Disc: Political Geography and Statistics
The Disc consists of four major landmasses and a lot of smaller islands. The four major continents are:
- The Central Continent, an un-named landmass which is substantially larger than the others. This includes Ankh-Morpork and the greater number of the named political states, and most of the action of the books occurs here.
- Klatch, a sub-continent comprising regions and states such as Howondaland and Hersheba. This is an ethnic melting pot known to have brown-skinned people analogous to Roundworld Arabs. Further Rimwards/south, in Howondaland proper, are plains known to accommodate a red-skinned people not unlike North American Indians, and rimward of them are jungles and savannahs where black-skinned people live. There is also a hint from several novels and writings that a forgotten colony of white people, left over from days of Empire, may complete the ethnic mix.
- Fourecks, or XXXX, which is either a colony or a very large island, depending on your point of view, populated by amazingly laid-back people who drink a lot of lager and eat meat-pie floaters.
- The Counterweight Continent, or Agatea, populated by an incredibly old, sophisticated, inward-looking and above all, cruel civilization, with a penchant for building walls round everything.
Significant island states include:
The population of the Disc has been estimated as twenty million. The estimate was made by the God Om, who in common with other gods (a) should know; and (b) should have an interest in the theoretical total maximum of believers it is possible for a God to have.
It is unclear whether this total includes Dwarves, Trolls and other races, or just the human population of the disc. However, as Om is a God of the human race, trolls have their own deities, and Dwarves don't bother with that sort of formal religion, Om is probably only counting humans (as they are the only people he's interested in).