Arrakis

The non-canon Dune Encyclopedia (1984) theorizes that the depletion of the oceans (the primary result of which was desertification) was probably caused by the impact or near miss of a comet or other quasi-planetary body. This event caused the loss of much of the atmosphere of Arrakis, allowing most of the oxygen and water to escape into space. This is thought to have occurred approximately 50 million years before the Imperium's creation. This catastrophic loss of oxygen led to the extinction of nearly all native flora and then therefore the fauna.

The Encyclopedia also explains that one of the few forms to survive were tiny worms of the phylum Protochordata. One of these forms was Shaihuludata, a genus of anaerobic burrowing worm that was the basal species from which the giant sandworms (Geonemotodium arraknis or Shaihuludata gigantica) evolved. Rather than sandworm creating desert, it was desert that created sandworm. The mass extinction of all of its predators and competitors for food allowed the animal, in a manner somewhat analogous to the evolution of unique faunal forms on isolated Terran islands, to take the evolutionary path that would not only re-oxygenate the Arrakeen atmosphere, but also create the spice melange with all of its immense consequences for humanity.

Finally, the Encyclopedia notes that early in the history of Arrakis, the Imperium made several attempts to terraform the planet, which resulted in an abundance of Terran desert life on the planet (such as kangaroo mice and hawks), but failed to otherwise change the environment, as the local sandtrout "encyst" any open water on the planet.

Frank Herbert's own Children of Dune, however, establishes that the sandtrout were brought to Arrakis from elsewhere. In the 1985 novel Chapterhouse: Dune, Chapterhouse is turned into a desert planet by transplanting sandtrout there.

The Zensunni wanderers, driven from planet to planet, eventually found their way to Arrakis, where they became the Fremen. They settled in artificial cave-like settlements known as sietches across the Arrakeen deserts. They also developed stillsuit technology, allowing them to survive in the open desert. By harvesting melange, they were able to bribe the Spacing Guild for privacy from observation and weather control in order to hide from the Imperium their true population and their plans to terraform Arrakis. Much of this ecological activity took place in the unexplored southern latitudes of the planet. The best-known of the sietches is Sietch Tabr, home of Stilgar and Muad'Dib's center of operations before victory in the Battle of Arrakeen put Muad'Dib on the Imperial throne.

According to the Legends of Dune prequel trilogy by Brian Herbert and Kevin J. Anderson, it was a group of Zensunni wanderers escaping slavery on the planet Poritrin who originally crashed on Dune in a prototype interstellar spacecraft several years prior to the creation of the Spacing Guild.

In Dune, Sietch Tabr is a major Fremen sietch originally led by Naib Stilgar. Paul Atreides and his mother Lady Jessica, safely escaping from the Harkonnen attack, come upon Sietch Tabr and are eventually accepted into the community. In these Fremen Paul finds an incomparable fighting force who are already disgruntled by Imperial rule. He shapes them into a resistance movement that eventually takes control of Arrakis, allowing Paul to depose the Emperor. Paul moves his base of operations to Arrakeen, but Sietch Tabr remains a center of Fremen culture and politics, as well as a religiously significant site for those who worship Paul as a messiah. All Fremen sietches but one are abandoned after the terraforming of Arrakis, their exact locations remaining a mystery for thousands of years.

During the reign of Muad'Dib until the ascension of his son Leto II, the Atreides home-base was a colossal megastructure in Arrakeen, designed to intimidate, known as the Keep. In Dune Messiah, the fortress is described as being large enough to enclose entire cities.

In his 1985 short work "The Road to Dune" (published in the short story collection Eye),[11] Frank Herbert described the Grand Palace of Arrakeen (and other sites) during the reign of Paul Atreides:

Your walking tour of Arrakis must include this approach across the dunes to the Grand Palace at Arrakeen. From a distance, the dimensions of this construction are deceptive [...] The largest man-made structure ever built, the Grand Palace could cover more than ten of the Imperium's most populous cities under one roof, a fact that becomes more apparent when you learn Atreides attendants and their families, housed spaciously in the Palace Annex, number some thirty-five million souls [...] When you walk into the Grand Reception Hall of the Palace at Arrakeen, be prepared to feel dwarfed before an immensity never before conceived. A statue of St. Alia Atreides, shown as "The Soother of Pains," stands twenty-two meters tall but is one of the smallest adornments in the hall. Two hundred such statues could be stacked one atop the other against the entrance pillars and still fall short of the doorway's capitol arch, which itself is almost a thousand meters below the first beams upholding the lower roof.

Alia's Fane (or Alia's Temple) is the two-kilometer wide temple Paul-Muad'Dib built for his sister Alia between the events of Dune and Dune Messiah. Herbert described it in The Road to Dune:

If you are numbered among "the heartfelt pilgrims," you will cross the last thousand meters of this approach to the Temple of Alia on your knees. Those thousand meters fall well within the sweeping curves leading your eyes up to the transcendent symbols dedicating this Temple to St. Alia of the Knife. The famed "Sun-Sweep Window" incorporates every solar calendar known to human history in the one translucent display whose brilliant colors, driven by the sun of Dune, thread through the interior on prismatic pathways.

The Tyrant Leto II rules the universe from the Citadel, a fortress built in the Last Desert of the Sareer. The Sareer is flanked by the Forbidden Forest, home of the ferocious D-wolves, the guardians of the Sareer. Beyond that lies the Idaho River, across which a bridge spans that leads to the festival city of Onn (once Arrakeen). Mount Idaho had been completely demolished to provide the raw materials to build the high walls surrounding the Sareer.[12] The Citadel itself is taken apart in the Famine Times after the death of Leto II in search of his alleged hoard of spice.

All Imperial cities on Arrakis are in the far-northern latitudes of the planet and protected from the violent weather of Arrakis by a natural formation known as the Shield Wall. When the Harkonnens controlled the planet, they ruled from the Harkonnen-built "megalopolis" of Carthag, described by Jessica as "a cheap and brassy place some two hundred kilometers northeast across the Broken Land."[4] Arrakeen was merely the titular capital until the arrival of the Atreides.

There are other cities scattered in the northern regions of the planet (especially near the ice cap, where water is harvested), as well as the Fremen sietch communities scattered throughout the desert.

Other notable sites on Arrakis throughout its history include Observatory Mountain, Mount Idaho, Dar-es-balat and the Kynes Sea.