The Golden Gate is located on the eastern side of Jerusalem's Wall. The Gate's structure is from the seventh century, which means it predates the Turkish wall which we know today. Remains of an even older gate dating to the time of the Second Temple were found.
The gate divided into two gates, both blocked today with bricks. The northern gate is called the northern gate is called the 'Gate of Grace' and the southern gate is called the 'Gate of Mercy'.
The Christian tradition marks The Golden Gate as the gate through which Christ entered Jerusalem, and that is why the gate is also names the 'Golden Gate'. That tradition also tells that this gate is where the byzantine emperor Heracles entered Jerusalem after freeing it from the Persians during the 7th century (a short while before the city was taken by Muslims).
The Golden Gate we can see now was originally built around 640 CE by either the last of the Byzantine rulers or the earliest Arab conquerors. References to some sort of gate located on the eastern wall of Jerusalem and near the Temple can be traced back much farther. When Herod rebuilt the Temple area, he probably rebuilt a gate here, but that would have been destroyed by Titus in 70 CE.
The Jewish tradition tells that The Golden Gate is the gate through which the Messiah will enter Jerusalem, bringing the Jewish nation to redemption. The emperor Suleiman, who heard this tradition, decided to prevent the arrival of the Messiah by blocking the gate with bricks, and by building a Muslim cemetery in front of the gate (the Messiahs is a Cohen, so he can not enter a cemetery...).
Today the gate's structure houses a Muslim prayer and study hall. Entrance to the gate is from the Temple Mount only.
The Golden Gate is one of the few sealed gates in Jerusalem's Old City Walls, along with the Huldah Gates, and a small Biblical and Crusader-era postern located several stories above ground on the southern side of the eastern wall.