Hadith
Sayyiduna Abu Hurayra 
reports that Rasulullah :saw: once said,
‘Have you heard of a city whose one side is on the sea and the other on land?’ The Sahaaba (Radhiallaahu Anhum) replied, ‘Yes, Oh Messenger of Allah :saw:’
Rasulullah :saw: then said,
‘Qiyaamah will not come until 70,000 from the Banu Ishaaq do not attack it. And when they will arrive, they will not use any weapons. Instead, they will recite ‘Laa ilaaha illallaahu wallaahu akbar’ and one side of the city will collapse.
Then they will repeat it for the second time and the other side
will collapse, and when they will say it for the third time, they will
be able to enter and collect the booty.
While they would be doing so, they will hear an announcement that the Dajjaal has appeared, so they will leave everything and return.’
(Sahih Muslim Hadith 7262)
Commentary
Imaam Nawawiy and others have stated that this refers to
the city of Constantinople.
They also state that in some narrations the words,
‘children of Ismaa’eel’ are mentioned and this refers to the Arabs.
(refer Sharhun nawawiy vol.9 pg.250-252;
Takmilah Fathul Mulhim vol.6 pg.336-337)