Question: Is there only one Hell or are there several Hells? And do they exist now?
Hell consists of seven levels. Disbelievers (kafirs) will be tormented in one of the levels of Hell according to their states.

It is written in the book Faraid-ul fawaid:
Hell consists of seven levels, which are one below another. The fire of each level is more vehement than that of the level above it. The Believers whose sins have not been forgiven will burn in the first level as much as their sins. Then they will be brought forth from Hell and will be taken to Paradise.

Various disbelievers will burn eternally in the other six levels.

Both Paradise and Hell exist now. According to some scholars, it is not known precisely where Hell is. But according to some others, it is below the seven layers of the earth. Since the earth, the sun, and all stars are in the first sky, there is the first sky below the seven layers of the earth no matter in what part of the earth we are. It is understood that Hell is in one of the seven heavens (skies).

Every Muslim knows that …
Do Paradise and Hell exist today?
Every Muslim knows that Hadrat Adam, the first human and the father of all humans, lived in Paradise for years. When he ate from the forbidden tree, he was sent to the earth. There are many verses in the Qur’an al-karim on this subject, such as Al-Baqara (35-36), Al-A’raf (17-27), Ta Ha (117-119). It is also stated in the Qur’an al-karim that Paradise and Hell are ready and are waiting for Believers and disbelievers respectively:

(Run to Paradise, which has been prepared for the pious and which is as wide as 
[the whole of] the heavens and the earth.) [Al-i ‘Imran 133]

(Beware of the Hellfire, which has been prepared for disbelievers.) [Al-i ‘Imran 131]

When our master the Prophet was ascended to the heavens, he toured Paradise and Hell as well, and he later related the things that he had seen. Some of them are as follows:

(I entered Paradise and saw domes of pearls.) [Muslim]

(On the Night of Mi’raj, I saw on the gate of Paradise written, “Reward for giving alms is ten times and reward for loaning is eighteen times.”) [Ibn Majah]

(On the Night of Mi’raj, I looked at Hell and saw those who were eating putrid carcasses. I asked who they were. Jabrail ‘alaihis-salam said, “They are those who ate the flesh of humans by backbiting them.”) [Imam-i Ahmad]

Where is Paradise?
Question: Is it possible that Paradise is on one of the planets that we know?
All stars and all planets we know today are in the first layer of the heavens (skies), and the heavens are composed of seven layers. It is reported that the other layers are much larger than this sky, which we know. There is information about Paradise in the Qur’an al-karim and hadith-i sharifs. The Qur’an al-karim says that the width of Paradise is as much as the width of the earth and the heavens. (Al-Hadid 21)

Therefore, it is not possible for Paradise to be on one of the planets. Paradise is in the higher heavens. (Daylami)

Eight paradises
Question: What are the names of eight paradises?
Dar al-Jalal,
2. Dar al-Karar,
3. Dar as-Salam,
4. Al-Khuld,
5. Al-Ma’wa,
6. Al-Adn,
7. Al-Firdaws,
8. An-Naim.