After the battle with the Romans, which ended with the conquest of Constantinople, the Dajjaal will appear, and Jesus son of Mary will descend from Heaven to the earth, to the white minaret in the east of Damascus, at the time of Salaat al-Fajr (the morning prayer), as we shall see in the Saheeh Traditions.
Dhoo Mukhammar said,
"The Prophet (صلى الله علیه وسلم) said, 'You will make a peace-treaty with the Romans, and together you will invade an enemy beyond Rome. You will be victorious and take much booty. Then you will camp in a hilly pasture; one of the Roman men will come and raise a cross and say "Victory to the Cross", so one of the Muslims will come and kill him. Then the Romans will break the treaty, and there will be a battle. They will gather an army against you and come against you with eighty banners, each banner followed by 10,000 men.' " [Ahmad, Abu Daawood, Ibn Maajah] 
Yusayr ibn Jaabir said,
"Once there was a red storm in Kufah. A man came who had nothing to say except, 'O 'Abd Allaah ibn Mas'ood, has the Hour come?' 'Abd Allaah was sitting reclining against something, and said, 'The Hour will not come until people will not divide inheritance, nor rejoice over booty.' Pointing towards Syria, he said, 'An enemy will gather forces against the Muslims and the Muslims will gather forces against them.' I asked, 'Do you mean the Romans?' He said, 'Yes. At that time there will be very heavy fighting. The Muslims will prepare a detachment to fight to the death; they will not return unless they are victorious. They will fight until night intervenes. Both sides will return without being victorious; then many will be killed on both sides. On the fourth day, the Muslims who are left will return to the fight, and Allaah will cause the enemy to be routed. There will be a battle the like of which has never been seen, so that even if a bird were to pass their ranks, it would fall down dead before it reached the end of them. Out of a family of one hundred, only one man will survive, so how could he enjoy the booty or divide any inheritance? While they are in this state, they will hear of an even worse calamity. A cry will reach them: "The Dajjaal has taken your place among your offspring." So they will throw away whatever is in their hands and go forward, sending 10 horsemen as a scouting party. The Prophet (صلى الله علیه وسلم) said, 'I know their names, and the names of their fathers, and the colours of their horses. They will be the best horsemen on the face of the earth on that day.' " [Ahmad, Muslim] 
Abu Hurayrah said,
"The Prophet (صلى الله علیه وسلم) said, 'The Hour will not come until the Romans camp at al-A'mash or Dabeeq. An army, composed of the best people on earth at that time, will come out from Madinah to meet them. When they have arranged themselves in ranks, the Romans will say, 'Do not stand between us and those who took prisoners from amongst us. Let us fight with them.' The Muslims will say, 'No, by Allaah, we will never stand aside from you and our brothers.' Then they will fight. One-third will runaway, and Allaah will never forgive them. One-third will be killed, and they will be the best of martyrs in Allaah's sight. One-third, who will never be subjected to trials or tribulations, will win, and will conquer Constantinople. Whilst they are sharing out the booty, after hanging their swords on the olive-trees, Satan will shout to them that the Dajjaal has taken their place among their families. When they come to Syria, the Dajjaal will appear, while they are preparing for battle and drawing up the ranks. When the time for prayer comes, Jesus the son of Mary will descend and lead them in prayer. When the enemy of Allaah (i.e. the Dajjaal) sees him, he will start to dissolve like salt in water, but Allaah will kill him.' " [Muslim] 
The Prophet (صلى الله علیه وسلم) said,
"The Hour will not come until the furthest border of the Muslims will be in Bulaa."[/i] Then he said, "O 'Alee!" 'Alee said, "May my father and mother be sacrificed for you!" The Prophet (صلى الله علیه وسلم) said, "You will fight the Romans, and those who come after you will fight them, until the best people among the Muslims, the people of al-Hijaaz, will go out to fight them, fearing nothing but Allaah. They will conquer Constantinople with Tasbeeh and Takbeer (saying "Subhaan Allaah" and "Allaahu Akbar"), and they will obtain booty the like of which has never been seen - they will share it out by scooping it up with their sheilds. Someone will come and say, 'The Dajjaal has appeared in your land', but he will be lying. Anyone who takes notice of him will regret it, and anyone who ignores him will regret it." [Ibn Maajah] 
Naafi' ibn 'Utbah said,
"The Prophet (صلى الله علیه وسلم) said, 'You will attack Arabia, and Allaah will enable you to conquer it. Then you will attack Persia, and Allaah will enable you to conquer it. Then you will attack Rome, and Allaah will enable you to conquer it. Then you will attack the Dajjaal, and Allaah will enable you to conquer him.' " [Muslim] 
When Mustawrid al-Qurashee was sitting with 'Amr ibn al-'Aas, he said,
"I heard the Prophet (صلى الله علیه وسلم) say, 'The Hour will come when the Romans will be in the majority.' 'Amr asked him, "What are you saying?" He said, "I am repeating that which I heard from the Prophet (صلى الله علیه وسلم)." 'Amr said, "If you say this, it is true, because they have four good characteristics: they are the most able to cope with tribulation, the quickest to recover after disaster and to return to the fight after disaster, and are the best as far as treating the poor, weak and orphans is concerned. They have a fifth characteristic which is very good; they do not allow themselves to be oppressed by their kings." 
The Prophet (صلى الله علیه وسلم) said,
"You will fight the Romans, and Believers from the Hijaaz will fight them after you, until Allaah enables them to conquer Constantinople and Rome with Tasbeeh and Takbeer ("Subhaan Allaah" and "Allaahu Akbar"). Its fortifications will collapse, and they will obtain booty the like of which has never been seen, so that they will share it out by scooping it up with their shields. Then someone will cry, 'O Muslims! The Dajjaal is in your country, with your families', and the people will leave the wealth. Anyone who takes notice will regret it and anyone who ignores it will regret it. They will ask, 'Who shouted?' but they will not know who he is. They will say, 'Send a vanguard to Ilyaa.' If the Dajjaal has appeared, you will hear about his deeds.' So they will go and see, and if they see that everything is normal, they will say, 'No-one would give a shout like that for no reason, so let us go together to Ilyaa'.' If we find the Dajjaal there we will fight him together, until Allaah decides between us and him. If we do not find the Dajjaal, we will go back to our country and our families.'" 
Mu'aadh ibn Jabal said,
"The Prophet (صلى الله علیه وسلم) said, 'The building of Bayt al-Maqdis (in Jerusalem) will be followed by the destruction of Yathrib (Madeenah), which will be followed by the conquest of Constantinople, which will be followed by the appearance of the Dajjaal.' Then he put his hand on the thigh or the shoulder of the one with whom he was speaking (i.e. Mu'aadh), and said, 'This is as true as the fact that you are here (or as true as you are sitting here).' " 
This does not mean that Madeenah will be destroyed completely before the appearance of the Day, but that will happen at the end of time, as we shall see in some authentic Ahaadeeth. But the building of Bayt al-Maqdis will be the cause of the destruction of Madeenah, as it was proven in the Hadeeth that the Dajjaal will not be able to enter Madinah. He will be prevented from doing so because it is surrounded by angles bearing unsheathed swords. 
Abu Hurayrah said,
"The Prophet (صلى الله علیه وسلم) said about Madeenah: 'Neither plague nor the Dajjaal can enter it.' " [Bukhaaree] 
 Similar Hadeeth in Abu Daawood, Kitaab al-Malaahim, (Hadeeth 4271), 11/397/399. Ibn Maajah, Kitab al-Fitan (Hadeeth 4089), 2/1369. Ahmad, Musnad, 9104.
Checker's Note: Saheeh, Saheeh al-Jami as-Sagheer: 3612.
 Muslim, Kitaab al-Fitan, 8/177, 178. Ahmad, Musnad, 1/384, 385.
 Muslim, Kitaab al-Fitan, 8 - 175, 176.
Al-A'mash is a place outside the city, and Dabeeq is a market-place in the city. "The city" refers to Aleppo (some say Damascus).
 Ibn Maajah, Kitaab al-Fitan (Hadeeth 4094), 2 - 1370.
The one who believes the liar will regret it, because he will find that the Dajjaal is not there. The one who does not believe him will regret it because the Dajjaal will appear soon afterwards.
Checker's Note: Fabricated. The reason is Kathir ibn `Abdillah, who is declared a liar by Abu Daawood and Shaafi'ee. He narrates a fabricated collection of hadeeth.
 Muslim, Kitaab al-Fitan wa Ashtaar al-Saa'ah, 8 - 178. Ibn Maajah, Baab al-Malaahim (Hadeeth 4091), 2 - 1380.
 Muslim, Kitaab al-Fitaan, 8 - 176.
 Al-Haythamee, Majma' al-Zawaa'id. Ibn Maajah, 7:248.
Checker's Note: Fabricated. Same reasons as the previous one. Reported by al-Bazzar, Kashful Astar bi Zawa'id al-Bazzar of al-Haythamee: 3386.
 Hasan, al-Mishkat, 1st checking: 5424.
 Abu Daawood, Kitaab al-Malaahim (Hadeeth 4273), 11 - 400, 401; Ahmad, Musnad, 5/245.
Checker's Note: Hasan.
 Bukhaaree, Kitaab al-Fitan, 9/76.