Far Tower
From Halopedia, the Halo wiki
The Far Tower was a Covenant tower in the Holy city of High Charity.
The tower featured some Holo-Pedestals, a Gravity Lift and three landing pads for Phantoms and dropships. The tower was connected to the Mausoleum of the Arbiter by a solitary bridge. This is where the High Prophet of Truth boarded a Phantom to reach the Forerunner Dreadnought with his captives, Miranda Keyes and Sgt Johnson.
The tower is also where the High Prophet of Mercy was attacked and killed by a Flood Infection Form, then was denied rescue, and was abandoned by Truth and his brute guards.
In Halo 2, it was the second location the player appeared in on the level High Charity. A Pelican crashed onto the tower platform and Flood Combat Forms emerged from the wreckage, followed by Brutes from a door to combat the newly arrived Flood.
It is certain that the Far Tower was destroyed along with the rest of High Charity at the end of the Human-Covenant War.