This question doesn’t have a brief answer. Please click on the detailed answer.
After proving the existence of Heaven and Hell, another important discussion refers to their location. This question has existed since ancient times and has been brought up amongst many different religions. It has been narrated from various traditions that a Jewish man asked Imam Ali (a) that: “Where are Heaven and Hell located? He replied: “Heaven is in the skies and Hell is in the earth.” 
So now the question is brought up as to where Heaven and Hell are located at. So when the discussion comes up as to its location, length, and properties we have to realize that the whole subject relates to an alternate non material world and the only way to gain knowledge of its particulars is through the Holy Quran and traditions which all come from an unseen source.
As for the existence of Heaven and Hell there are many traditions and verses about this subject.  Scholars, through their research of traditions, have come to the conclusion that Heaven will be above the ‘Seven Heavens’ and Hell will be in the ‘Seventh Earth’.  The question which remains is if the meaning of earth and skies which is used in these traditions is the apparent and literal meaning or has another meaning. Of this question no answers have yet been found. In the Holy Quran the term ‘Heavens’ has been used for many various meanings:
“Sama” in the Quran:
The word “sama” and its derivatives have been mentioned in the Quran 310 times in which have been used for two meanings:
a) A materialistic meaning:
The Quran has used this word (sama) for its materialistic meaning in many instances, such as:
1) Meaning upwards: اصلها ثابت و فرعها فی السماء “…whose root is firmly fixed, and its branches (reach) to the sky” 
2) Meaning the atmosphere surrounding the earth: “ و نزلنا من السماء ماءً مبارکاً” “And we send down from the sky blessed rain” 
3) Meaning space, the place where the stars and other planets are located: “Blessed is He who made constellations in the skies, and placed therein a lamp and a moon giving light” 
b) A spiritual meaning:
The Holy Quran has also used the word "sama" in its spiritual meaning many times:
1) Meaning the level of “nearness” and “presence” in which this world’s affairs are originally managed from: “He directs the affairs from the sky to the earth” 
As to the location of Heaven and Hell there are some differing opinions:
1. It is in the heavens because the Holy Quran gives the news of the ‘Ascent’ of the Holy Prophet (s) towards the heavens and says: “Close to which is the Garden of Tranquility” Heaven is where the Lote tree is, which is the highest point in the sky. 
2. Heaven and Hell are not material and hence they do not have a need for a physical location or place. When the Day of Judgment takes place, then the earth and skies will become enmeshed in each other, but Heaven and Hell will remain as they were.
3. Heaven and Hell are the internal and external aspects of this very world. 
Conclusion: To conclude, this is a matter which relates to the non material and non physical world and in the traditions and verses of the Holy Quran, for whichever reason, it has not been mentioned clearly, and hence we are not able to make a definitive conclusion about this matter.
For further research please refer to:
1. Question 812 (site: 972) (The existence of Heaven and Hell at this current time).
2. Question 7903 (Site: 8011) (The reality of Heaven and Hell).
3. Question 7685 (Site: 7765) (The Heaven on Prophet Adam (a)).
 Deylami, Irshadul-Qulub (translation of Rezai), pg. 178.
 The website for Iranian scholarly papers, Ja’far Sobhani.
 Biharul-Anwar , vol.8, pg. 205.
 جعل فی السماء بروجاً و جعل فیها سراجاً و قمرا منیراً Furqan:61.
 یدبّر الامر من السماء الی الارض Sajdah:5.
 See: Mohammad Taqi Mesbah Yazdi, Ma’arefe Quran (Dar Rahe Haqq Press, Qom, 1367), pg. 234, and: Dr. Mohammad Ali Rezai Esfehani, Pejoohesh dar E’jaze Elmiye Quran (Mubin Press, Rasht, 1st printing, 1380) v.1, pg.134.
 Surah Najm, Verse 15.