The Forerunners created large Anti-gravity gondolas, that travel by utilizing anti-gravity technology to ferry individuals over long and extensive distances, that are otherwise difficult to traverse.
So far, three types of gondolas have been discovered throughout the Halo universe, the first near the Temple, (the Temple gondola) and the second near the Library, (the Library Gondola) and thirdly, one inside Requiem (the Requiem gondola). Anti-gravity gondolas have appeared only on Installation 05 and in Requiem.
The Temple gondolas and the underwater elevators are the only way to reach Regret's temple. These gondolas use anti-gravity "tethers" below and above it. The library gondolas and the Teleportation Grid are the only way to reach Installation 05's Library. Like both previous gondolas, the Requiem gondola is the only way to get to the other side of a communications spire within Requiem.
The Temple Gondola is traveled upon in the level Regret in Halo 2. John-117 used this during his mission to destroy Delta Halo. It cannot be stopped manually, though it automatically stops when docking to either boarding platform.
The library gondola is traveled upon in the level Quarantine Zone in Halo 2. It is started automatically by the player character Arbiter in a cutscene. It automatically stops when docking to either docking station.
The Requiem gondola is used in the level Shutdown, when John-117 must get to the other side of a communications spire within Requiem so that he can deactivate the Ur-Didact's Cryptum's shields. It stops at several points due to enemy interference and must be restarted.