Where are Heaven and Hell?
This chapter of the Vishnu Purana describes the distances to the various Lokas above the Earth:
The sphere of the earth (or Bhúr-loka), comprehending its oceans, mountains, and rivers, extends as far as it is illuminated by the rays of the sun and moon; and to the same extent, both in diameter and circumference, the sphere of the sky (Bhuvar-loka) spreads above it (as far upwards as to the planetary sphere, or Swar-loka). The solar orb is situated a hundred thousand leagues from the earth; and that of the moon an equal distance from the sun. At the same interval above the moon occurs the orbit of all the lunar constellations. The planet Budha (Mercury) is two hundred thousand leagues above the lunar mansions. Śukra (Venus) is at the same distance from Mercury. Angáraka (Mars) is as far above Venus; and the priest of the gods (Vrihaspati, or Jupiter) as far from Mars: whilst Saturn (Sani) is two hundred and fifty thousand leagues beyond Jupiter. The sphere of the seven Rishis (Ursa Major) is a hundred thousand leagues above Saturn; and at a similar height above the seven Rishis is Dhruva (the pole-star), the pivot or axis of the whole planetary circle. Such, Maitreya, is the elevation of the three spheres (Bhúr, Bhuvar, Swar) which form the region of the consequences of works. The region of works is here (or in the land of Bhárata).
Above Dhruva, at the distance of ton million leagues, lies the sphere of saints, or Mahar-loka, the inhabitants of which dwell in it throughout a Kalpa, or day of Brahmá. At twice that distance is situated Janaloka, where Sanandana and other pure-minded sons of Brahmá, reside. At four times the distance, between the two last, lies the Tapo-loka (the sphere of penance), inhabited by the deities called Vaibhrájas, who are unconsumable by fire. At six times the distance (or twelve Crores, a hundred and twenty millions of leagues) is situated Satya-loka, the sphere of truth, the inhabitants of which never again know death.
Note that "league" is just how they're translating the word "Yojana". Also, the order of these Lokas from lowest to highest is Bhuloka (where we live), Bhuvarloka, Svarga (i.e. Devaloka or heaven), Maharloka, Janaloka, Tapoloka, and Satyaloka (i.e. Brahmaloka). (These are the seven Lokas we mention in the Pranayamam mantra, if you've ever done Sandhyavandanam.)
In any case, if we go by what the translator tells us in a footnote, then the realm of Devaloka extends from a distance of 100,000 Yojanas all the way up to the pole star.
Now this chapter describes the seven Patala Lokas beneath the Earth:
The extent of the surface of the earth has been thus described to you, Maitreya. Its depth below the surface is said to be seventy thousand Yojanas, each of the seven regions of Pátála extending downwards ten thousand.... Below the seven Pátálas is the form of Vishńu, proceeding from the quality of darkness, which is called Śesha, the excellencies of which neither Daityas nor Dánavas can fully enumerate. This being is called Ananta by the spirits of heaven, and is worshipped by sages and by gods. He has a thousand heads, which are embellished with the pure and visible mystic sign: and the thousand jewels in his crests give light to all the regions.
And then this chapter describes the realms of Yamaloka, where people are punished for sins, and which lie below the seven Patala Lokas and Vishnu's serpent Adiseshan:
I will now, great Muni, give you an account of the hells which are situated beneath the earth and beneath the waters, and into which sinners are finally sent.
The names of the different Narakas are as follows: Raurava, Śúkara, Rodha, Tála, Viśasana, Mahájwála, Taptakumbha, Lavańa, Vimohana, Rudhirándha, Vaitaraní, Krimíśa, Krimibhojana, Asipatravana, Krishńa, Lálábhaksha, Dáruńa, Púyaváha, Pápa, Vahnijwála, Adhośiras, Sandansa, Kálasútra, Tamas, Avíchi, Śwabhojana, Apratisht́ha, and another Avíchi. These and many other fearful hells are the awful provinces of the kingdom of Yama, terrible with instruments of torture and with fire; into which are hurled all those who are addicted when alive to sinful practices.
It's also worth noting that Yamaloka is described as lying to the South, whatever that means. For instance, in this chapter of the Kishkindha Khanda of the Ramayana, when Sugriva gives instructions to the Vanaras on how to search for Sita in different directions, he says that if they keep proceeding South they'll eventually reach Yamaloka:
After that, farther from earth there is the most dreadful world of manes, namely the abode of Yama, the Terminator, and you need not consider going there. You can go or search only up to this point, oh, the best braving vanara-s, as that world of manes will be encompassed with an alarming darkness, and it is the capital city of Yama, the Terminator. After that there is no entry into the abode of Yama for the mortals.
I should add that while these passages discuss spatial separations, personally I don't think these Lokas are actually in our physical universe; in addition to spatial separation they might also be located in separate universes, but that's just speculation on my part.
Note: “The question: Where are Heaven and Hell?” is licensed by Stack Exchange Inc (https://hinduism.stackexchange.com/); user contributions licensed under CC BY-SA.