Causeways are bridges built by the Forerunners to span large canyons. Unlike the light bridges on Halo, causeways appear to be made of metal. They are supported by light cables attached to each canyon's walls. They also have supports much like that of a truss arch bridge.
Causeways appear in a variety of designs. Most commonly, the causeway will have two levels. They have also been observed with one level or three levels. On Installation 04, the causeways featured two levels, with glass floors on both levels. The glass floors on the top level were breakable, allowing you to drop down to the bottom level of the causeway. The bottom level's glass floors featured impenetrable glass.
Causeways were seen by John-117 during the UNSC's operations on the surface of Installation 04, with several spanning the canyons near the Control Room. On the Ark, one of the cooling systems was located on a three level causeway.
Causeways are quite common on Requiem, although they were usually the one level variant, with a two level causeway connecting the Cartographer with the Cathedral.
There are several causeways throughout the Halo games. Causeways appear in the levels Assault on the Control Room and Two Betrayals, and in the multiplayer level Gephyrophobia from Halo: Combat Evolved. There is a single level causeway in the level The Great Journey in Halo 2. In Halo 3, the multiplayer level Narrows also takes place on top of a causeway. In Halo 4, there are numerous smaller one level causeways scattered throughout the game, with a two level one connecting the ends of the Forerunner complex in Requiem.
- Halo: Combat Evolved (First appearance)
- Halo 2
- Halo 3
- Halo Wars
- Halo: The Flood
- Halo Encyclopedia
- Halo 4