Harvest space elevators

The 7 Harvest Space Elevators were responsible for transporting cargo and humans between the orbital platform Tiara and Harvest's capital city of Utgard. The elevator system, along with the planet's shipping operations were maintained by the AI Sif.

History
During the First Battle of Harvest the elevator system was used to evacuate the remaining population, after the Covenant began glassing the planet. After the Tiara was destroyed, the Space Elevators collapsed to the surface and wrapped themselves around the planet. The strands were later buried by Mack to protect them from the Covenant's plasma bombardment.

Trivia

 * Harvest having 7 Space Elevators is yet another seven reference.