There are structures in Nuusra that were built thousands of years before the Sangheili joined the Covenant. In 2558, Olympia Vale surmised that some of these structures were "ancient history" before the Pyramids were built on Earth.
Battle of Nuusra
At some point before October 27th, 2558, the remnants of Jul 'Mdama's Covenant arrived in the area, preparing for an imminent attack against the Swords of Sanghelios who controlled the territory, as well as most of the planet. During the battle, human forces raided some of the local ruins on their way to the Arbiter, battling against multiple waves of Covenant forces. Some of the ancient Sangheili ruins were damaged forever, as both warring sides used them as provisional bases for cover.
When a Guardian emerged during the Arbiter's victory at the Battle of Sunaion nearby, he and his surviving Swords retreated back to Nuusra and established a makeshift camp in its cliffs to hide from the emergent Created and their Guardian enforcers. It was here they regrouped with other surviving members of the UNSC that were seeking shelter.
Nuusra is mainly composed of arid and desert environments, being much different from the nearby city of Sunaion, which is a city primarily composed of communities built above water surfaces. The territory is almost entirely covered in rocky valleys and canyons.
Locke with a BR85 battle rifle.
Buck with an MA5D assault rifle.
Tanaka with an M395B DMR.
Vale with an M20 SMG.
Locke engaging a Type-58 Wraith with a plasma caster.
Thel 'Vadam communicating with Fireteam Osiris.