It seems to be mostly similar to Earth, though with various differences, the main one being that it has two moons instead of one. Said moons are called the Viola Moon and the Cello Moon. Ar Ciel is located in a still unnamed galaxy and orbits around a mother star called Sol.
Its surface used to have all kinds of topography, environments, and weather, which had a very large influence in the formation of the cultures that developed in each region. However, 700 years ago, because of the Grathnode Inferia disaster, the surface was covered by the Sea of Death and the sky was sealed off by the plasma sea called the Blastline. Now, the only inhabitable areas are the floating lands located near each one of the three Towers of Ar tonelico.
At the present, there are only three regions known in this planet, which are the places where each one of the three Towers were built:
Possibly there were other regions and countries, but because of the total destruction of the planet's surface due to the Grathnode Inferia, no inhabitable areas remain except for the three Towers. However, it's also known that there was a region called Justine within the territories of Sol Cluster, but it was destroyed in the Seven Bloodstains Incident, various years before the Inferia.
The Wills of the Planet
As every single being in the universe of Ar tonelico, the planet Ar Ciel has a Will too, however, it's composed of an aggregate of several high-leveled consciousnesses, each one having an specific role and function in the maintenance and preservation of the life in the planet. Due to their great powers, the inhabitants of Ar Ciel worship them as Gods and the Wills themselves have also manifested in the physical world, either by possessing a person, or by being born as a human, to help with the development of the human civilization, as well trying to keep it from overpopulating the planet's surface. While the Planet has a theoretically infinite number of wills, the main wills that compose its consciousness are listed in the following table:
|Name||Name in Kanji and Meaning||Lineage||Role in the Myths||Current Role as a Will||Represents in Cartology|
|Ciela = Horus||(Doesn't have one).||Land||Discovered near the end of the First Era. Doesn't appear in any myths.||Governs the entirety of the Ar Ciel's physical structure (D-Wave phenomena)||N/A|
|Nayudara = Juklizda||
(Creator of Myriads)
|Sky||Sun god||Light, radiation, preservation of the stratosphere||January / First Moon|
|Rokkan = Clyuue||
|Souls||King of kings, lord of the gods||Core of the wills, controller of U waves||February / Second Moon|
|Soutentei = Soreile||
(Blue Heaven Emperor)
|Sky||God of the skies and wind||Weather control, atmospheric maintenance||March / Third Moon|
|Koudeinomikoto = Listea||
(Lord of the Crimson Shrine)
|Souls||God of weapons and battle||Control of H-Wave interference, mediation, natural selection||April / Fourth Moon|
|Saranoyomei = Shelanoir||
(Master of the Sal Tree World)
|Land||God of plants, forests, and life||Plant-centric god of creation||May / Fifth Moon|
|Deiji = Dijya||
|Sky||God of mountains and volcanoes||Oversees mantle convection, minerals, the earth, etc.||June / Sixth Moon|
|Reishiki = Lere (Rere)||
(Princess of Zero Beasts)
|Land||God of souls and the material world||Primary god of creation, controls H-Waves||July / Seventh Moon|
|Sakiyarumei = Saki||
(Shining Life That Blooms at Night)
|Land||God of salvation, life||Animal-centric god of creation||August / Eighth Moon|
|Datenkou = Salapator (Sarapatra)||
(Fallen Heaven Empress)
|Souls||Goddess of love, god of downfall||H-wave interference, harmony, resonance||September / Ninth Moon|
|Soumanomiya = Soma||
(Residence of the Blue Measles)
|Sky||Violent god of catastrophes||Balance through natural selection, maintenance of the world||October / Tenth Moon|
|Sashanomiya = Sasya (Sasha)||
(Residence of Gold Dust)
|Souls||God of civilization and knowledge||Oversees D-waves and material order||November / Eleventh Moon|
|Suzunomiya = Hymmnosphere||
(Residence of the Milky Way)
|Souls||God of song and creation||Mother of all 3D substance, controls D-waves||December / Twelfth Moon|
|Kokura = Filament||
|Sky||God of death and poverty||Overseer of balance for world preservation||N/A|
|Gurentei = Yurishica||
(Crimson Lotus Emperor)
|Land||God of fire and civilization||Revelation and encouragement of human advancement||N/A|
|Ar Ru||(Doesn't have one).||Land||Born after the First Era. Doesn't appear in any myths.||Creation and control of the Antibodies.||N/A|
Note: The first name is the one given to them by the humans, while the second name is their true name. Additionally, while Ciela is indeed a representation of the Will Horus, she is also composed of several other Wills, Clyuue and Juklizda included among them. It's just that Horus forms the core of her existence.
As shown in the table above, all of the Wills belong to a determinate Lineage, which indicates to which Wills they are subordinate, or more straightforwardly, which Wills are parents to which. All of the Wills can have their origins traced back to the three Wills of Origin: Horus, Juklizda and Clyuue, which were the first Wills of Ar Ciel, and the founders of the Earth, Sky and Soul lineages, respectively. However, if any of the Wills of Origin were to die, then all of the Wills that are children to it would perish as well. This is what would happen a few years after the events of Ar tonelico Qoga: Knell of Ar Ciel to Horus due to her extreme weakening, which was caused by the planet's surface being destroyed by the Grathnode Inferia. In this same example, if Horus dies, all the other Land Wills will perish as well, and this will inevitably lead to the death of the planet and every being living in it, in the event called the Demise of Ar Ciel.
The Wills are divided into two main classes: Modifiers, which are tasked with creating life, and Maintenancers, which are the ones tasked with the preservation of life; and among them, they are also further subdivided into other four subclases: Powers (the Wills of Power), Wisdomes (the Wills of Knowledge), Charities (the Wills of Love), and finally, Hymmers (the Wills of Feelings). They can also change classes depending on the circumstances in which the Planet is at the moment, if they really wish to undergo said change and if the other Wills are in agreement with the change. However, the Will that requests this has to comply with a great number of very severe conditions to be able to perform the change, otherwise, it won't gain the approval of the other Wills, and will disappear. Once a Will has disappeared, it's impossible to bring it back, and another one has to be created in replacement for it.
The Wills of Ar Ciel all live in the Planetary Core, which, as its name says, it's located in the deepest underground areas of the planet.