A Porta is a sphincter-like orifice embedded into the floors and walls of Flood hives that acts as the Flood analog to doorways. Portas were sighted in the Flood-infested High Charity, in the Halo 3 multiplayer map Isolation, and on the Flood dens in Halo Wars.
- Portas are comprised of seven segments, and there are seven Portas on the level Cortana.
- The name "porta" probably comes from the Greek word porta (πόρτα), which means "door".
- On the Halo 3 multiplayer map Isolation there is one Porta. Sliding down a hole on the top part of the map will lead the player to slide down a tube. A Porta will open, leading into a Flood-infested cave.
- It is possible that Portas are not directly controlled by the Gravemind, as they always open for John-117 even when it is clear that the Gravemind does not want him to progress further.