From Halopedia, the Halo wiki
Epsilon Expanse was a massive gorge on the human colony of Draetheus V. It had nine bridges connecting the gorge to allow access to a southern plateau. During the Battle of Draetheus V, Merg Vol's Covenant engaged the UNSC's 23rd Armored Cavalry and Spartan Sarah Palmer at Epsilon Expanse. Although the Scorpion tanks were destroyed by Covenant artillery fire, Palmer and a small amount of UNSC Marines safely made it across the bridges. After crossing the bridges, the UNSC destroyed the artillery and took control of Epsilon Expanse. The Expanse was later used as an escape path for Elephants from Faraday Base.
List of appearances