In regards to the city of Mystery Babylon, Rev. 18:7 says, "How much she hath glorified herself, and lived deliciously, so much torment and sorrow give her: for she saith in her heart, I sit a queen, and am no widow, and shall see no sorrow." 

I could see how this Bible passage might fit the Vatican City as Mystery Babylon because she thinks she is not a widow because she considers herself to be the Bride of Jesus Christ, who is her bridegroom and future husband. Therefore, she thinks she will be "no widow" and "shall see no sorrow" because her bridegroom Jesus Christ is supposed to rapture her and take her to heaven to escape great tribulation. Also since the Lord Jesus Christ is called the King of Kings in Rev. 19:16, she would be His Queen. I think the city of Mystery Babylon who says in her heart, "I sit a queen and am no widow and shall see no sorrow" describes the Catholic church and religion whose headquarters is in the Vatican City which was once a part of Rome. They also consider the Virgin Mary the Queen of Heaven and pray to her like she is a god when the real queen of heaven was a pagan goddess in Jeremiah 7:18, 44:17-19, 25. 

On the other hand, I don't see why the city of Mecca with its Muslim religion would consider itself to be a queen and no widow because there is nothing in their Koran that says their god Allah has a bride or a wife.  Allah is no kingand he has no queen.