The exact location of hellfire is known by God only although it was described thoroughly in the Quran and Hadith of prophet Mohamed peace be upon him. Some of the descriptions are in the following:

Al-Hasan said:
"While he was on the pulpit – the pulpit of Al-Basrah – `Utbah bin Ghazwain narrated that the Messenger of Allah (s.a.w) said: “Indeed a giant rock can be thrown from the brink of Hell and it will continue to fall into it for seventy years without reaching the bottom of it.”.He said: “`Umar used to say:'Increase in your remembrance of the Fire, for its heat is extreme, its bottom is distant, and its whips are of Iron.'” (Sahih)

حَدَّثَنَا عَبْدُ بْنُ حُمَيْدٍ، حَدَّثَنَا حُسَيْنُ بْنُ عَلِيٍّ الْجُعْفِيُّ، عَنْ فُضَيْلِ بْنِ عِيَاضٍ، عَنْ هِشَامٍ، عَنِ الْحَسَنِ، قَالَ قَالَ عُتْبَةُ بْنُ غَزْوَانَ عَلَى مِنْبَرِنَا هَذَا مِنْبَرِ الْبَصْرَةِ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏ "‏ إِنَّ الصَّخْرَةَ الْعَظِيمَةَ لَتُلْقَى مِنْ شَفِيرِ جَهَنَّمَ فَتَهْوِي فِيهَا سَبْعِينَ عَامًا وَمَا تُفْضِي إِلَى قَرَارِهَا ‏"‏ ‏.‏ قَالَ وَكَانَ عُمَرُ يَقُولُ أَكْثِرُوا ذِكْرَ النَّارِ فَإِنَّ حَرَّهَا شَدِيدٌ وَإِنَّ قَعْرَهَا بَعِيدٌ وَإِنَّ مَقَامِعَهَا حَدِيدٌ ‏.‏ قَالَ أَبُو عِيسَى لاَ نَعْرِفُ لِلْحَسَنِ سَمَاعًا مِنْ عُتْبَةَ بْنِ غَزْوَانَ وَإِنَّمَا قَدِمَ عُتْبَةُ بْنُ غَزْوَانَ الْبَصْرَةَ فِي زَمَنِ عُمَرَ وَوُلِدَ الْحَسَنُ لِسَنَتَيْنِ بَقِيَتَا مِنْ خِلاَفَةِ عُمَرَ ‏.‏


In the Quran communications between the people hellfire and Paradise are mentioned (that might suggest that paradise and hellfire are close to each other although parameters are different in the Hereafter).

7:50 Al-A'raaf

‎وَنَادَىٰ أَصْحَابُ النَّارِ أَصْحَابَ الْجَنَّةِ أَنْ أَفِيضُوا عَلَيْنَا مِنَ الْمَاءِ أَوْ مِمَّا رَزَقَكُمُ اللَّهُ ۚ قَالُوا إِنَّ اللَّهَ حَرَّمَهُمَا عَلَى الْكَافِرِينَ

And the dwellers of the Fire will call to the dwellers of Paradise: "Pour on us some water or anything that Allah has provided you with." They will say: "Both (water and provision) Allah has forbidden to the disbelievers."