The House is described as being the centre of the Universe, with seven primary parts and access to any of the Secondary Realms. Originally created by The Architect, The House, whilst having no absolute certain layout is consisted of 7 diverse areas, each governed by one of the Trustees. The areas consist of ( going by the order of the books from lowest to highest) The Lower House, The Far Reaches, The Border Sea, The Great Maze, The Middle House, The Upper House, and at the highest point of The House, The Incomparable Gardens. It is speculated by some that the order of the floors are instead The Border Sea, The Great Maze, The Far Reaches, The Lower House, The Middle House, The Upper House, and the Incomparable Gardens. This is just a theory to where The Border Sea and Great Maze go, but the other floors are known facts. However, during the events of Mister Monday, while conversing with the Old One, Atrthur is told that nothing, the void, exists close to the Coal seller, suggesting that the lower houses foundations exists within the void itself. Another consideration is the conversation between Arthus and Thursdays Dusk after taking possession of the fourth key; Arthur is told by Marshal Dusk that an elevator exists within "Sir Thursday's study [which] goes up to the Middle House and down to the Lower House," suggesting that the Great Maze exists between these two demesne. There are multiple ways in and out of the house, the most common being The Front Door, which in theory, can access almost any area of The House. Another way is via The Border Sea, and the Line of Storms, which can access, and be accessed via, any sea, lake, river, or expanse of liquid in any of the Secondary Realms. The House, along with all of existance, was destroyed when Nothing overran the last surviving aspect of the house - The Incomparable Gardens - and then rebuilt by the recently born New Architect, in nearly exactly the same way it was before.
The House was created by the divine figure known as the Architect, who created the House to record, without intervening on any behalf, all that happened in the Secondary Realms (a term used to describe the Universe at large). Most Denizens of the House believe that the House was created first, but this is only true of the Incomparable Gardens. Having created The House, The Secondary Realms, and a Law that would prevent Denizens from intervening in the actions of mortal creatures, the Architect vanished and was not seen again until the events in the Elysium.
The House's overall appearance is described as being a mix of a large number of different architectual styles, including arches, and other various building features. The House's appearance also makes it hard to look at or to try and follow the building outlines due to these building styles, as even Arthur, in Mister Monday, finds it hard and dizzying to look at the House.
House Time is constant, while time in the Secondary Realms is malleable; it is even able to flow backwards if a sufficient power, such as a Key to the Kingdom is used upon it. Thus, a day may pass on Earth while half a year will pass in the House. This inconsistency in time allows Arthur to spend large amounts of time in the House whilst 'Local Earth time' remains still. This occurs because the Front Door (the main method of transit between the House and the Secondary Realms) takes note of important people's travel (e.g. Arthur's passage through the Door) and alters the time it allows passage back accordingly. The system is not infallible; while Leaf is in the House, time continues as normal in the Realms (Sneezer states that the Door did not consider Leaf noteworthy enough to account for). This temporal system is not dissimilar to that used in the Chronicles of Narnia, wherein lengthy adventures or even lifetimes can be spent in Narnia's world while only seconds pass in ours.
Demesnes of the House
The House in comprised of seven demesnes, as follows:
The Lower House
The Lower House was the domain of Mister Monday. Due to Monday's affliction with Sloth its bureaucratic affairs became impossibly inefficient until Monday's loss of power, after which Dame Primus, as the Steward of Arthur's regime, has attempted to make the Lower House manageable. The remaining Morrow Days have attempted to impede this effort by swamping the Lower House with paperwork.
The Lower House is guarded by the Corps of Inspectors, by the robots known as Metal Commissionaires, by Denizen Commissionaire Sergeants, and by Midnight Visitors. These are under the control of the office of Monday's Dawn, Noon, and Dusk, respectively. 
Doorstop Hill, and on it the Front Door of the House, is located in the Lower House. The Front Door of the House is a means by which one may leave the House and enter a Secondary Realm, and vice versa. To enter it from the Secondary Realms, one must be able to see the House. It is a pair of wooden doors surrounded by constantly shifting wrought-iron patterns whose movements are mesmerizing to human eyes. The Door is guarded by the Captain Keeper; in his absence, the Lieutenant Keeper of the Door, as an ally of Arthur's, has guarded it ever since.
The Coal Cellar is a deep pit in the Lower House where Denizens that have been punished are sent to mine and shape coal for delivery to buyers within the House. The Old One is also imprisoned here. He is bound by two chains extending from a minute and hour hand on a clock face. Every time the clock strikes twelve, two clockwork figures appear and claw out his eyes. This is the punishment laid upon him by the Architect for his attempting to interfere in the Secondary Realms, which was directly forbidden by the Architect. His escape is impossible; according to Monday's Dusk, the Seven Keys combined could not free him. In Lady Friday, Dr. Scamandros mentions that something odd is happening in the Coal Cellar; not with the Old One, but the collectors. The nature of what is happening is not stated. It is revealed in Superior Saturday that flowers have started growing around the Old One's clock-face prison, and that his clockwork torturers have been destroyed by the Old One and that he will soon be able to escape.
The Seven Dials is a set of seven grandfather clocks in a room accessible from Monday's Dayroom, the main office of the Lower House. Using them, one can travel to the current time in any given Secondary Realm. Thus far, only Sneezer, Monday's butler, has operated them. When the Lower House was consumed by Nothing, Dr. Scamandros says that the Seven Dials would move themselves to safety, but did not reveal where they have gone.
Nearly all of the Lower House was destroyed by Nothing that had leaked from the dam in the Far Reaches, being unleashed by Superior Saturday. The bulwark between the Lower House and the Far Reaches only lasted a few hours, during which important records and some Denizens were saved. However, the bulwark eventually collapsed and the Lower House was devoured. Only part of the Deep Coal Cellar survives, due to the protections around the Old One's prison; but it is slowly dissolving as the prison weakens.
The Far Reaches
The Far Reaches was the domain of Grim Tuesday. Originally, the Far Reaches was a Grand Cavern, and in the Cavern was a steady spring of Nothing. Tuesday used the Nothing to create items, such as Commissionaires and Not-Horses, which he sold to other demesnes of the House. His greed however, drove him to deepen and widen the spring in an effort to find more Nothing. In time, the spring became a vast Pit, which eventually becomes the whole of his demesne, sparing only his Treasure Pyramid and the train station where his personal train into the Pit docks. Grim Tuesday used indentured slaves from his own demesne, as well as ones from other Morrow Days sent to him as payment, to mine the useful amounts of Nothing. The Pit is extremely dangerous as it has been dug deep into the foundations of the House and is very close to breaching into the void of Nothing beyond. After Grim Tuesday was deposed, Dame Primus received regency over the Far Reaches and ordered their Denizens to fill the Pit, but was unable to have this task completed before the Far Reaches were destroyed by a wave of Nothing released by Superior Saturday. The entire demesne was consumed by the wave of Nothing in four to five minutes. The Immaterial dam wall was breached by sorcerous drills. During the interim before this event, many of the things produced by Grim Tuesday for the other demesnes had become scarce as a result of the cessation of production caused by Dame Primus' orders.
The Border Sea
The Border Sea was an ocean previously under the rule of Drowned Wednesday. After Wednesday transformed into a leviathan and submerged into the sea, the sea overflowed nine-tenths of all land in the demesne including Port Wednesday. A new port was partially prepared on Wednesday's Lookout before this deluge. Any of the buildings that were submerged were transformed into ships, which thereafter sailed the Border Sea along with Wednesday’s original fleet of 49 ships. A unique aspect of the Border Sea is that anything that is lost accidentally, but not stolen, will appear in it.
The Border Sea extends into any body of water in the Secondary Realms, and therefore can be a means of travelling anywhere. The Line of Storms, a series of vicious lightning storms, guard the entrance into the sea; only an express invitation into the Sea will prevent the Line from killing people instantly. Raised Rats live here and pilot their steamships. Pirates also live here, of whom the most formidable was a mortal pirate who somehow passed the Line of Storms into the Border Sea, Elishar Feverfew. Feverfew was a trained House sorcerer, and was trained in several dark arts. He used Nothing very indiscriminately and had been changed by this Nothing into something not quite human or Denizen.
At the end of Drowned Wednesday, Wednesday’s Dawn informed Arthur that much of the Sea had extended into the Void of Nothing, and since Wednesday used all of the Key’s power keeping her shape, had not reigned it in. As Arthur does not wish to use the Keys unless absolutely necessary, he left this task to his Steward Dame Primus. As of Superior Saturday, the Sea has yet to be brought under control. In Lord Sunday it is revealed to be destroyed by a wave of nothing.
The Great Maze
The dominion of Sir Thursday. Now in possession of the New Architect. The Great Maze was the fourth demesne that Arthur gained control of as the Rightful Heir. The Great Maze is the base of the Glorious Army Of The Architect. It is a giant maze of 1000 one miles squares each with its own habitat. Once a day the tiles change position, making the maze hard to navigate. Only a few of the tiles are in permenant positions, such as the Citidal and Weapons Armoury etc.
The Middle House
The dominion of Lady Friday, now in possession of the New Architect. The Middle House was the fifth demesne that Arthur gained control of as the Rightful Heir. The Middle House, alike its Lower and Higher counterparts manage the administration of the records. Friday's Scriptorium is the base of operations.
The Upper House
The dominion of Superior Saturday, now in possession of the New Architect. The Upper House was the sixth demesne that Arthur gained control of as the Rightful Heir. The Upper House, alike its Lower and Middle counterparts manage the administration of the records. It also is the only demesne that has Sorcerers. It also deals with the training of sorcerers.
The Incomparable Gardens
The dominion of Lord Sunday. Now in possession of the New Architect. Contrary to what was originally thought, the Incomparable Gardens was in fact the epicenter of the universe, as opposed to the House itself. The Incomparable Gardens was the seventh and final demesne that Arthur gained control of as the Rightful Heir. The Incomparable Gardens, like the name suggests, are a garden. According to many Denizens in the house, it is the most beautiful place in The House. It holds many exhibits that Lord Sunday has chosen to house there, primarily taken from the Secondary Realms. It is also the HQ of the ruler of the house during the books. This is also the final demesne to be destroyed. The Incomparable Gardens can be thought of as Eden, as it shares numerous similarities with it.