Far Tower
From Halopedia, the Halo wiki
The Far Tower was a Covenant tower in the holy city of High Charity. It featured some Holo-Pedestals, a Gravity Lift and three landing pads for Phantoms. This is where the High Prophet of Truth boarded a Phantom to reach the Forerunner Dreadnought and where the High Prophet of Mercy was attacked and killed by a Flood Infection Form. It was connected to the Mausoleum of the Arbiter by a solitary bridge.
In Halo 2 it is the second location you appear in on the level High Charity. A Pelican crashes and Flood Combat Forms emerge from the wreckage, followed by 2 Brutes (Rank depends on difficulty) from a door to combat the newly arrived Flood.
It is almost certain that the Far Tower was destroyed along with the rest of High Charity at the end of the Human-Covenant War.