Crimson Hell (紅蓮地獄 Guren Jigoku) is the first level of Impel Down in which prisoners are kept. The level houses the least-infamous prisoners and contains a large forest of red trees. The leaves of the trees, known as Kenju (剣樹 bladed tree), are as sharp as blades, while the grass on the floor, the Haribarisō (針々草 needle grass), is as spiky as needles.

Here, prisoners are forced to run through the forest while being chased by poisonous spiders and guards to experience all the pain from being cut from all directions. As a consequence of prisoners being forced through this forest, it is soaked in blood.

Deep within the forest is a hole that leads to Level 2. For those who do not wish to live through the pain of being cut any longer, they were given the option of jumping down the hole to Level 2, which contains an even more terrifying hell that nobody is willing to risk. The security here is somewhat lax, as a prisoner can sneak smalls things into this area, such as an Black Den Den Mushi into your cell.

Wild Beast Hell (猛獣地獄 Mōjū Jigoku) is the second level of Impel Down in which prisoners are kept. The criminals on this level are not small fry and each, at least, a bounty of 15,000,00 Million. This place is larger than level one but that is due to the jailers. It contains various wild beasts of sorts, they given the title of jailers or guard dogs. Some noteable beasts kept here include Puzzle Scorpions and Manticores. Puzzle Scorpions are large poisonous insects that can join together to become giant centipedes, their tier being 3. Manticores are man-eating human faced lions that will devour everything from their prey including the bones, their tier is also 3 . Their human faces allow them to speak. However, they can only imitate what they hear like parrots as they do not understand what they are actually speaking. The words they speak are mostly things they heard from the prisoners so some of the things that they say are completely out of place. Among these regular-sized beasts kept here are also two gigantic beasts, the Basilisk and the Sphinx who both are tier 4.

The Basilisk is a gigantic snake born from a chicken. It is a feathered mutant that possesses both snake and chicken traits. Though formidable, the Basilisk is not the most powerful beast in the level. It is considered to be the "second-in-command".

The Sphinx is a gigantic human faced feathered lion. Significantly larger than the Basilisk and much more fearsome than the other beasts, it is considered the "boss" of the level and is charged with guarding the stairway that leads out of the level. It is so fearsome that the prisoners kept in the level, and even the other beasts hide from it. Like the Manticores, it is capable of imitated speech. It randomly says the names of types of noodles and apparently understands the concept of giving thanks before meals. It is such a strong beast that it is capable of breaking the floor beneath it if it hits it enough times.

With these various beasts, prisoners kept here are forced to be chased by them through the corridors of the level. Because of the fearsome danger, prisoners often either lose the will to go on, or refuse to escape even when their cells are unlocked.

Starvation Hell (飢餓地獄 Kiga Jigoku) is the third level of Impel Down in which prisoners are kept. Most of the prisoners kept here are pirates who have a bounty of Beli50,000,000 or higher. On this level, prisoners feel the heat rising up from Level 4 and are given precious little food and water to keep them in a near death state. They are reduced to the point where, by merely looking at them, one cannot tell that they were ever once frightening criminals. Also while the temperature here is nothing compared to level below, it is intense enough to cause overwhelming dryness, resulting in Level 3's somewhat desert-like terrain.

In the middle of the level is a large hole going directly to Level 4 down below. This, combined with a gigantic fan directly above the hole, serves as the main ventilation system to redirect the smoke produced from below. Level 4 can be reached through this hole; however, to travel down it holds a risk of death or scalding by the fire and heat from the floor below. Due to the heat there is an constant drain of stamina each post, it being 5.

Blazing Hell (焦熱地獄 Shōnetsu Jigoku) is the fourth level of Impel Down in which prisoners are kept. At this level, a pool lies filled with boiling blood heated by a raging fire making it extremely hot. The heat caused by this is so intense that it also heats up the level directly above it. If one tries to jump down to this level from Level 3 using the large hole used for ventilation above but do not land in a safe place, then they will die.

Prisoners from other levels are regularly tortured here. The most prevalent form of torture however is being thrown into the gigantic pot of boiling blood in the middle of the level. Other tortures involve prisoners being hung from ropes around their stomachs en masse and being dangled over the raging flames throughout the level, and being put to back-breaking hard labor by suppling giant logs of firewood to keep the flames going. Guards on this level must don protective gear to avoid being hurt by the intense heat, as it is strong enough to sear bared flesh.

The warden of Impel Down, stays here. His office contains a lift, which can take several people to all the levels throughout the fortress, bypassing the stairs. This is also where the kitchen of the prison is located, right next to The Warden's office. There is a constant drain of Stamina for criminals here, it being 10 stamina every three posts.

Freezing Hell (極寒地獄 Gokkan Jigoku) is the fifth level of Impel Down in which prisoners are kept. This is the level where criminals with bounties of Beli100,000,000 and over are kept. In stark contrast to the level above it, the entire level here is a giant freezer. The level is so cold that not only do the prisoners kept here either freeze to death or lose pieces of their flesh from severe frostbite, but the food given to them is frozen to the level of being virtually inedible. Due to the extreme cold, Den Den Mushi do not function in this level, thus cutting off both contact and surveillance, except on the locations localized around the entrances that connects Level 5 to the previous and next levels. Along with the severe cold, the level is inhabited by wolves. These wolves roam around the level like the beasts of Level 2, where they were originally stationed at. However, they proved to be too brutal to be in Level 2 as they also hunted the other beasts as well, including the Basilisk and the Sphinx.

Eternal Hell (無限地獄 Mugen Jigoku) is the lowest level of Impel Down. It is where prisoners who are insanely powerful, have caused crimes extremely atrocious, and/or whose mere existences have become a major threat to the World Government itself are kept. One of the Admirals said even a single Level Six prisoner lurking in a remote country could be an incredible danger to the public. The prisoners on this level have been given either the death penalty or a life sentence. They are basically "erased" from history.

Most high-ranking officers of Impel Down tend to avoid this level because of the danger these criminals pose, but will visit it if the need arises. The chief warden of Impel Down also has the authority to execute prisoners kept here on the spot if they begin acting up, and may do so at their own discretion.

Though the prisoners on this floor are either jailed for the rest of their lives or until their execution day arrives, some prisoners may be given a temporary sentence for reasons unknown.

Interestingly enough, even though Level 6 is considered the worst hell, prisoners kept here are never actually tortured. Though Minotaurus occasionally showed up and tormented the prisoners with their clubs. It simply seems to be a holding cell for life or until an execution and prisoners do not have to endure terrible conditions (burning heat, freezing cold, etc.) unlike the higher floors. Some prisoners are put here due to them not being affected by the tortured on the other levels. Although, solitary imprisonment has been proven to be an effective torture in the real world.