Jerusalem is considered to be the holiest city by all 3 Abrahamic faith namely Christianity, Islam & Judaism.
In last few days, it has again come into limelight after US president, Donald Trump declared it as a capital city of Israel which got criticism and condemnation from several countries and massive protest by Palestinians who also regard it as their capital.
The bone of contention is a rock which in on top of a natural hill (mount Moriah for christians, mount Marwah for muslims & mount Moriyya for jews).
Greeks around 657 BCE founded Byzantium. It was significant because of its strategic location that connected it to east and also in terms of defence. it could only be attacked from the west as rest sides were covered with sea.
Because if its prominent location and fertile land, it was marred with wars in the early times. It was a centre of Persian wars between Greeks and Persians. Persians were hell bent on conquering Greece and city kept changing hands between Persians and Greeks. It was later conquered by Spartans who made peace with Persians (Persian king Xerxes) and provided their full support to Persians in exchange of letting them govern Byzantium.