As mentioned above, the underworld is divided into two parts: Tatalos and Ilisija, ruled by Hades and Persephone respectively. Tatalos is actually what we usually call "hell", which is divided into several layers. Here I will make a very simple explanation.
The gates of hell stand at the entrance to hell. The inscription on the gate is as follows:
Through me into the lonely city,
Through me into eternal sadness,
Through me, in the abandoned race.
A sense of justice moved my sacred builder;
The divine omnipotence created me,
The highest wisdom is combined with the first love.
Before me, only eternal things were created,
I will exist forever,
When you enter, give up hope forever.
Not far from the gate of hell, we came to the river of hell, the first prison. There are all kinds of dead people crowded on the river bank. Charon, the ferryman of Akron River, is responsible for ferrying them across the river. However, those who have never done anything wrong or done nothing all their lives can't cross the river. They can only groan and wander around the Akron forever.
Judge Minos sat at the entrance of the second prison. He will decide which prison to send the dead according to their crimes before they die. The second prison itself holds people who commit crimes because of lust. A biting cold wind blows all the year round.
It is raining cold in the third prison. This is where gluttony is punished. They will be torn apart by three giant dogs Cerberus.
The fourth prison is a place where greedy people and profligate people are held. After their death, they are still crazy about money and will never get peace.
After the fourth prison, I came to Styx, where the fifth prison is located. The souls of irritable people tear at each other here. Styx is the most famous river in hell. People who have soaked in the river are invulnerable. If any god swears in the name of this river, but breaks his oath, he will become dumb.
The last three prisons are too numerous to describe simply, so they are omitted here. You can refer to Dante's Divine Comedy if you are interested.