From Halopedia, the Halo wiki
The Fenyot Basin was a location on the human Inner Colony world of Reach.
During the SPARTAN-II's training, the candidates played month long games of sniper elimination and stealth tag among the hoodoo maze there.
By October 7, 2559, the Banished had taken control of the basin. On October 7 itself during Operation: WOLFE, Seraphs launched from there to chase the Owl UNSC Special Delivery.