There were / are 3 valleys in the low terrain south of Jerusalem. One to the southeast was the valley of Jehoshaphat, also called the valley of decision or judgment.
"Then I have gathered all the nations, And caused them to go down unto the valley of Jehoshaphat, And I have been judged with them there, Concerning My people and Mine inheritance -- Israel, Whom they scattered among nations, And My land they have apportioned." (YLT)
" Multitudes, multitudes [are] in the valley of decision, For near [is] the day of Jehovah in the valley of decision." (YLT)
The middle valley connected to the west end of the valley of Jehoshaphat, was the valley Hinnom, or valley of the sons of Hinnom, in the Greek Gehenna.
Josh. 18:16, in describing the southern boundary of the tribe of Benjamin,
"and the border hath come down unto the extremity of the hill which [is] on the front of the valley of the son of Hinnom, which [is] in the valley of the Rephaim northward, and hath gone down the valley of Hinnom unto the side of Jebusi southward, and gone down [to] En-Rogel, " (YLT)
Josh. 15:8, describing the northern boundary of Judah,
"and the border hath gone up the valley of the son of Hinnom, unto the side of the Jebusite on the south (it [is] Jerusalem), and the border hath gone up unto the top of the hill-country which [is] on the front of the valley of Hinnom westward, which [is] in the extremity of the valley of the Rephaim northward;" (YLT)
Keil and Delitzsch Biblical Commentary at Josh. 15:14 still discussing the boundary of Judah states,
"It then went up into the more elevated valley of Ben-hinnom, on the south side of the Jebusite town, i.e., Jerusalem (see at Joshua 10:1), and still farther up to the top of the mountain which rises on the west of the valley of Ben-hinnom, and at the farthest extremity of the plain of Rephaim towards the north. The valley of Ben-hinnom, or Ben-hinnom (the son or sons of Hinnom), on the south side of Mount Zion, a place which was notorious from the time of Ahaz as the seat of the worship of Moloch (2 Kings 23:10; 2 Chronicles 28:3; 2 Chronicles 33:6; Jeremiah 7:31, etc.), is supposed there, but of whom nothing further is known (see Robinson, Pal. i. pp. 402ff.). The plain of Rephaim (lxx γῆ Ῥαφαείν, in 2 Samuel 5:18, 2 Samuel 5:22; 2 Samuel 23:13 κοιλὰς τῶν Τιτάνων), probably named after the gigantic race of Rephaim, and mentioned several times in 2 Sam. s a battle-field, is on the west of Jerusalem, and is separated from the edge of the valley of Ben-hinnom by a small ridge of rock. It runs southwards to Mar Elias, is an hour long, half an hour broad, and was very fertile (Isaiah 17:5); in fact, even to the present day it is carefully cultivated (see Rob. Pal. i. p. 323; Tobler, Topogr. v. Jerus. ii. pp. 401ff.). It is bounded on the north by the mountain ridge already mentioned, which curves westwards on the left side of the road to Jaffa. This mountain ridge, or one of the peaks, is "the mountain on the west of the valley of Hinnom," at the northern end of the plain referred to." Source: here
The repeated tradition that the valley of Hinnom was a garbage dump with fires that never ceased burning is in question.
From "The Fires of Gehenna: View of Scholars" by Todd Bolen,
"The first is Edward Robinson, preeminent explorer of the Holy Land beginning in 1838. He wrote:
“In these gardens, lying partly within the mouth of Hinnom and partly in the Valley of Jehoshaphat, and irrigated by the waters of Siloam, Jerome assigns the place of Tophet; where the Jews practised the horrid rites of Baal and Moloch, and ‘burned their sons and their daughters in the fire.’ It was probably in allusion to this detested and abominable fire, that the later Jews applied the name of this valley (Gehenna), to denote the place of future punishment or the fires of hell. At least there is no evidence of any other fires having been kept up in the valley; as has sometimes been supposed” (Biblical Researches, vol. 1 , 404-5).
"The origin of the “garbage dump” theory appears to be Kimchi. James A. Montgomery observes this medieval commentator’s logic, but does not accept it.
“With the common sense which often characterizes Jewish commentators, Kimchi says that the place was the dump of the city, where fires were always kept burning to destroy the refuse; ‘therefore the judgment of the wicked is parabolically called Gehenna.’ But from the Biblical references the place appears to have nothing physically objectionable about it; in contrast to its contemporary condition Jeremiah prophesied that it would one day be called ‘Valley of Slaughter’” (“The Holy City and Gehenna,” JBL 27/1 , 34)." Source: here
As O. Nicholas has already mentioned, The valley of Hinnom is also referred to by the name "Tophet".
Isa. 30:33, in the judgment pronounced of Assyria,
"For, arranged from former time is Tophet, Even it for the king is prepared, He hath made deep, He hath made large, Its pile [is] fire and much wood, The breath of Jehovah, As a stream of brim stone, is burning in it!" (YLT)
Jer. 7:30-32, God's anger against Judah,
"30 For the sons of Judah Have done the evil thing in Mine eyes, An affirmation of Jehovah, They have set their abominations in the house On which My name is called -- to defile it,
31 And have built the high places of Tophet, That [are] in the valley of the son of Hinnom, To burn their sons and their daughters with fire, Which I did not command, Nor did it come up on My heart.
32 Therefore, lo, days are coming, An affirmation of Jehovah, And it is not said any more,
The Tophet,' And Valley of the son of Hinnom,' But `Valley of the slaughter,' And they have buried in Tophet -- without place." (YLT)
Tophet is Stong's Heb. 8612 "Topheth" and is a place name located south of Jerusalem in the valley of Hinnom.
From Brown-Driver-Briggs - "others think Aramaic = fire-place... from Jer. 7:32, a burial place. Source: here
There is a reference included in Wikipedia's information on Gehenna (which I find interesting) based upon an article from a 2005 issue of Biblical Archeological Review, 35:4-5, "The Riches of Ketef Hinnom" by Gabriel Barkay that the valley of Hinnom had become a place of cremation.
"There is evidence however that the southwest shoulder of this valley (Ketef Hinnom) was a burial location with numerous burial chambers that were reused by generations of families from as early as the seventh until the fifth century BC. The use of this area for tombs continued into the first centuries BC and AD. By 70 AD, the area was not only a burial site but also a place for cremation of the dead with the arrival of the Tenth Roman Legion, who were the only group known to practice cremation in this region." Source: here
The valley of Hinnom is synonymous with funeral pyres, the place of burning and sacrifice - a crematorium, if you will.
On the west side of the valley of Hinnom was the valley of the Rephaim, or the valley of giants. It either ran adjacent on the west side of Hinnom, or at one time Hinnom was part of the valley of the Rephaim. (See Josh 15:8 and 18:16 above.)
Excerpt from McClintock and Strong Biblical Cyclopedia - Rephaim, Valley of:
"South of Mount Zion — the most southern part of the valley of Gihon — is called Wady Rafaath by the Arabs, which corresponds to Rephaim in Hebrew. Hence Schwarz infers that this is the true valley of Rephaim, though usually taken for that of the son of Hinnom (Palest. p. 240)" Source: here
Excerpt from Bible Hub Atlas - Rephaim, Vale of:
"It is located by Josephus between Jerusalem and Bethlehem (Ant., VII, iv, i; xii, 4). It corresponds to the modern el-Biqa`, which falls away to the Southwest from the lip of the valley of Hinnom. The name in ancient times may perhaps have covered a larger area, including practically all the land between Jerusalem and Bethlehem, where the head-waters of Nahr Ruben are collected." Source: here
The valley of the Rephaim was also where many battles with the Philistines were fought. (2 Sam. 5:18, 22; 23:13; 1 Chron. 11:15, 14:9).
References to the Rephaim became known as speaking of the dead (Psa. 2:18; 88:10; Prov. 9:18; 21:16; Isa. 14:9, among others). The giants had been slaughtered, and the use of that name became known for those who had died and been wiped out, desolated, destroyed (Deu. 3:11; Josh. 11:21-22; 14:13-15).
The Rephaim was symbolic of the state of dead and destroyed souls. The valley of the Rephaim, or the valley of giants might as well be called the valley of the dead.
So, we see a picture on a north directional map of an east to west (right to left) pattern of these valleys. The valley of decision (Jehoshaphat) on the east, the valley of funeral pyres (Hinnom) in the center, and on the west the valley of the dead (Rephaim). This pattern jumps out as judgment, then the burning altar, and finally the outer place - outer darkness of the dead.
I do not mean to imply that these valleys were/are the actual places of final judgment, only that the pattern shows the process.
Gehenna is not the final outcome. It is the lake of fire, or burning altar, or crematorium for those that are subject to the judgment. It does not mean eternal torment. It is the process of the second death, the final separation. And, the result is the soul is destroyed and gone, just like the Rephaim are gone.
"But the fearful, and unbelieving, and the abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death." (KJV)
"And be not afraid of those killing the body, and are not able to kill the soul, but fear rather Him who is able both soul and body to destroy in gehenna." (YLT)
The burning fire of Gehenna causes the second death.
"Even as Sodom and Gomorrha, and the cities about them in like manner, giving themselves over to fornication, and going after strange flesh, are set forth for an example, suffering the vengeance of eternal fire."(KJV)
Fire was always a symbol of God's judgment (Deu. 4:24; 32:22; Ezek. 38:19; Jer. 21:12; Heb. 12:29)
"He hath bent his bow like an enemy: he stood with his right hand as an adversary, and slew all that were pleasant to the eye in the tabernacle of the daughter of Zion: he poured out his fury like fire." (KJV)
As are many of the references in the OT, many of the references to fire in the NT are the symbol of God's judgment. The judgment of God is the first association we should make with the word "fire".
The never ceasing fire, the eternal fire is symbolic of God's never-ceasing and eternal judgment. Once He pronounces judgment it is an eternal judgment, and cannot be undone. So, as His fire / judgment is permanent, then those condemned to the second death have been permanently destroyed by the fire of God's judgment.
The traditional teaching of most churches that "hell" is a place of eternal torment is not hermeneutically sound. As the first death is a separation of the soul from the body, the second death is everlasting separation of the soul from God. It does not mean it is a state of permanent torment, although He will do whatever He decides with the condemned.
Once that sentence of judgment has been pronounced the separation is permanent / eternally and forever determined. The sentence of judgment is the eternal state / condition. What happens to that soul afterward ...we don't know. That is up to God. He mentions "outer darkness" in Matt. 22:13, and "mist of darkness" in 2 Pet. 2:17.
"And these will go away into everlasting punishment, but the righteous into eternal life.” (NKJV)
Everlasting punishment does not mean everlasting life. It means the punishment is meted out, and permanent. Everlasting death, everlasting separation is a state of darkness where there is no light. As nothing can live without light, the second death may very well indicate the permanent destruction of the condemned soul.
" And the city had no need of the sun, neither of the moon, to shine in it: for the glory of God did lighten it, and the Lamb is the light thereof. >24 And the nations of them which are saved shall walk in the light of it: and the kings of the earth do bring their glory and honour into it." (KJV)
The only ones who are promised eternal life are those that are in Christ, the Israel that is saved with an everlasting salvation (Mark 16;16; John 3:15; 6:54; 1 John 2:25; Gal. 3:26-29; Isa. 45:17). For if you are in Christ, then are you counted for Abraham's seed, and therefore you are the Israel of God which is saved forever.
Those that are not in Christ face the judgment, and what follows... the fire of gehenna, which causes the second death... the death of the soul.
I have more about the giants and the Rephaim at my blog here.
All bold emphasis is mine.
Additional map sources:
The Valley of Jehoshaphat - here
The Valley of Slaughter - here