Covenant watchtower
From Halopedia, the Halo wiki
Summary
The Covenant use deployable lookout towers when they set up fortified positions to alert them of advancing forces and to give their snipers an elevated view of the the battlefield.
They are basically a large platform suspended in the air by a medium-sized anti-gravity generator which is also used as a miniature Gravity Lift to ferry snipers and lookouts to and from the platform. In Halo 2, they appear in many campaign levels and a multiplayer level (Relic) also. The only two problems are that it's suicidal to stay there for a long time and you must jump out of the window in order to leave the tower.
The platforms are capable of being knocked off the gravity lifts with rockets. This is achieved by firing 2 rockets at the corner of the platforms, or, if available, keep firing Gauss blasts at it.It will end up falling off, this allows you to float on the gravity lift.
Glitch
On all gravity towers that have been knocked down, the base is still active, and can be used to push you up directly into the air from which you can continue to hover and snipe enemies.
