Babylon is a symbolic name of any city where godlessness reigns. Ive heard many including Athonite monks refer to NYC as Babylon.
But at the time of the NT, Rome was considered the new babylon(see 1Pet 5.13). Keep in mind that there are still monks (and many protestants) who interpret the events of Rev 17-18 to be speaking of the current papist church who are the inheritors of ancient roman rile. The babylon mentioned in Rev 17,18 has always been interpreted as Rome. You can look this up in the Orthodox NT (2vol set) under footnote (401) on Rev 17.12 where St Cyril of Jerusalem describes that 10 roman kings will come to power and an eleventh the antichrist will seize the roman power, the remaning kings will be subject to him.
Every source i have ever read interprets the Mystery Babylon to be Rome this includes Orthodox eschatological books like "Ultimate Things" and the OSB. Also Rome is pointed to thru a historical study.
It says the woman sits on 7 mountains (Rev 17.9). Rome was built around 7 hills. It says 5 (kings) have fallen, One is, the other has not yet come. The five that have fallen were Augustus thru Nero. Nero was slain but many thought he would come back to life(see Rev13.3).
The one that was most likely refered to Domition (others say his father Vespacian). The one who is yet to come , the antichrist, was believed to be a Nero revived (as mentioned above rev 13.3), hence the phraseology , "the beast that was and is not, is himself also the eighth(Rev 17. 11). In Rev 17.8 the same basic phrase :'The beast that you saw was and is not and will ascend out of the bottomless pit....". Anotherwords he was a king, at the time of writing he was not, but will once again reveal himself.
Jerusalem's judgement and destruction had already come when the Romans destroyed it, in their war from 66-72 a.d. Under the roman general Titus in 70 a.d. the temple was destroyed and finally the total city ransacked. This is why the Jerusalem Church fled to Pella in 66 a.d. heeding Christ's prophecys about the judgement of Jerusalem (see Matt 24.1-2, Lk 21.5-9, 20-24.)
In Revelations Jerusalem is still called the 'holy city' (Rev11.2) and the 'beloved city ' (Rev 20.9)