The priest who offered the Red Heifer on the Mount of Olives, sprinkled its blood seven times toward the Holy of Holies (Mishnah Parah 3.9). There must therefore have been a direct line of vision between the Mount of Olives and the entrance to the Temple.
There have been suggestions that this priest looked from the top of the Mount of Olives through the Golden Gate, but one could never see any Sanctuary, wherever one places the eastern gate on the Temple Mount, as that gate is located far too low down.
The level of the top of the Mount of Olives (810m) is 75m higher than the Temple platform (735m). The sill of the Golden Gate is located some 15m below the level of the Temple platform.
There is, however, a direct line of vision from the top of the Mount of Olives to the entrance to the Temple through the Nicanor Gate.