Where are Paradise and Hellfire located, and is it true that Hell is in the depths of the earth?

Scholars have explicitly stated that Paradise (Jannah) is in the seventh heaven, and Hellfire (Nar) is in the lowest earth. Imam Al-Bukhari narrated from the Prophet, peace and blessings be upon him, that Al-Firdaws is the middle and highest part of Paradise, and above it is the Throne of the Most Merciful. Al-Bayhaqi narrated with a weak chain of transmission from Ibn Mas'ud that Paradise is in the seventh highest heaven and Hellfire is in the seventh lowest earth. Some have cited verses as evidence, among them the Almighty's saying: "Nay! Verily, the Record of the wicked is in Sijjin." [Al-Mutaffifin: 7], and Sijjin is the lowest earth. Ibn 'Uthaymeen said: Paradise is in 'Illiyyin (the highest of high places), and Hellfire is in Sijjin, and Sijjin is in the lowest earth. He also stated that Hellfire is in the earth, but its exact location within the earth is not known.