Jerusalem is a city, so the question is nonsensical. In Jerusalem, the Temple Mount (Har Ha-Bayit or Haram Ash-Sharif) is sacred to both Judaism and Islam.
Al-Aqsa,Temple Mount, Al-haram Sharif
What is sacred to both are the Torah, Psalms, and the Old City of Jerusalem.
Christianity, Judaism and Islam.
Jerusalem
Judaism, Christianity and Islam. Though Islam doesn't view Jerusalem in the same manner as Judaism or Christianity. For Judaism and Christianity, Jerusalem is place of the world's foundation and the city where G-d's presence once rested. Islam's holy city is actually Mecca, in Saudi Arabia. Islam's claim to Jerusalem is political, not religious (or at least not at all in the way Christians and Jews view Jerusalem).
There is no such thing as the "Jerusalem Religion". Jerusalem is a city, not a set of beliefs. Although Judaism, Christianity, and Islam all hold Jerusalem to be sacred, none of these religions was founded in Jerusalem.
Yes, Jerusalem one of Islam's holiest cities.
For Judaism and Christianity it is Jerusalem. For Islam it is Mecca.
Judaism & Islam
Jerusalem
Jerusalem is located in Israel. It is one of the oldest cities in the world and holds religious significance for Judaism, Christianity, and Islam.