And there came one of the seven angels who had the seven vials and spoke with me [Apostle John], saying:Come, I will shew thee the condemnation of the ‘great harlot’ who sitteth upon many waters: (Rev. 17:1, Douay-Rheims Catholic Bible)
At dumating ang isa sa pitong anghel na may pitong mangkok, at nagsalita sa akin, na nagsasabi, Pumarito ka, ipakikita ko sa iyo ang hatol sa bantog na patutot na nakaupo sa maraming tubig; (Rev. 17:1, Tagalog Catholic Bible)
The "Great Harlot" [‘Great Whore’] in Revelation 17:1 symbolizes an "apostate religious system"(a perversion of true Christianity mixed with idolatrous paganism) that is already being spread in the world through a process known as 'Ecumenism'. The “apostate religious system” being formed will have come into full existence during the first 3-1/2 years of the Seven Year Tribulation Period.
(Note... Idolatrousworship is frequently represented in the Bible as a “harlot”, i.e., see Ezekiel 16:14-63 and Ezekiel 23:1-49.)
Please note here that the “Great Harlot” is “sitting upon many waters”, which is interpreted by the angel to Apostle John in Revelation 17:15 as being… “peoples, and multitudes, and nations, and tongues”…meaning that the “Great Harlot’sidolatrous forms of worship”already have great influence over the entire earth!
Most importantly in Revelation 17:1, the angel is going to show Apostle John in a vision the condemnation (destruction) of the “Great Harlot” (the apostate world-wide religious system) and this destruction will happen towards the end of the FIRST 3-1/2 YEARS of the Seven Year Tribulation Period.—We know this to be true because the entire world will be required to worship Antichrist and his "One World Religion" during the SECOND 3-1/2 YEARS of the Seven Year Tribulation Period.