It isn't, Jerusalem is one of the first city of our time when it was created in the Kingdom of Israel in 1,000 B.C. It holy because it is the mainframe of religious life of the Jews during that time. Christianity was formed in 1 A.D after the death of Christ.
Jerusalem is holy because many of the cultures was built in the city and the city is the culture foundation of Islam, Judaism, and Christianity.
You're not debating, you're outright saying things that you want to say and not providing your facts. You don't know if God is real, so please show me that God is really dead or does not exist? You see my point, I can throw that right back at you.