Square-Gates

Square-Gates are the Tri-Gates' counterpart in Halo 3.

Description
The Square-Gates are areas that are filled with shadows of squares. They have been found all over Sandtrap, and there are probably more on other maps. To see them on Sandtrap, find a way inside the walls of the map, whether it's through Pan Cam or the Forge Turret Glitch. Once inside the secret rooms, the Square-Gates should become apparent. You may need to overload the map first, though.

They also appear on the level, The Covenant, if you go to the Citadel area, and fly a Hornet out of the map, and then fly it behind the first tower, walking around out there, on the backs of the towers, there are some squares similar to the ones on Sandtrap. You can also see them by performing the Time Travel Glitch in the beginning of the level to go forward to the Citadel area, and then just look at the towers from the back.

Trivia

 * On Sandtrap, there are also Da Vinci Code Objects that are in the shape of squares underneath the map, as well as the eggs on the towers.