In the eleventh chapter of the Apocalypse we read:
 Then I was given a measuring rod like a staff, and I was told: "Rise and measure the temple of God and the altar and those who worship there,Many have sought to identify the two witnesses. Some say Moses and Elijah and some Preterists state that these two witnesses represent all the prophets and John the Baptist (e.g. Chilton). However, the Church Fathers identified them as "Henoch and Elias" or "Enoch and Elijah" (Augustine). The reason for this is that Enoch and Elijah are the two Old Testament saints who were assumed into Heaven prior to death. Neither of them died. Their future death will be a martyrdom under the hand of the eschatological Antichrist.
 but do not measure the court outside the temple; leave that out, for it is given over to the nations, and they will trample over the holy city for forty-two months.
 And I will grant my two witnesses power to prophesy for one thousand two hundred and sixty days, clothed in sackcloth."
 These are the two olive trees and the two lampstands which stand before the Lord of the earth.
 And if any one would harm them, fire pours out from their mouth and consumes their foes; if any one would harm them, thus he is doomed to be killed.
 They have power to shut the sky, that no rain may fall during the days of their prophesying, and they have power over the waters to turn them into blood, and to smite the earth with every plague, as often as they desire.
 And when they have finished their testimony, the beast that ascends from the bottomless pit will make war upon them and conquer them and kill them,
 and their dead bodies will lie in the street of the great city which is allegorically called Sodom and Egypt, where their Lord was crucified.
 For three days and a half men from the peoples and tribes and tongues and nations gaze at their dead bodies and refuse to let them be placed in a tomb,
 and those who dwell on the earth will rejoice over them and make merry and exchange presents, because these two prophets had been a torment to those who dwell on the earth.
 But after the three and a half days a breath of life from God entered them, and they stood up on their feet, and great fear fell on those who saw them.
 Then they heard a loud voice from heaven saying to them, "Come up hither!" And in the sight of their foes they went up to heaven in a cloud.
This fact is confirmed by Saint Thomas Aquinas in his Summa theologiae:
Reply to Objection 2. Elias was taken up into the atmospheric heaven, but not in to the empyrean heaven, which is the abode of the saints: and likewise Enoch was translated into the earthly paradise, where he is believed to live with Elias until the coming of Antichrist. (Summa theologiae III, q. 49, a. 5)Saint Thomas teaches that these two men are not in empyrean heaven (i.e. the supernatural realm) but are in the atmospheric heaven (outer space?). Whatever the situation, they are waiting for their encounter with the Antichrist. At least that's what Saint Augustine and Saint Thomas Aquinas teach--and it's difficult to argue with them.