Hidden Rebel Base
From Wookieepedia, the Star Wars wiki.
The Hidden Rebel Base was located on the planet Corellia and was one of the locations the Alliance High Command relocated to after the Battle of Yavin while looking for a more secret location. It was also used to recruit any new Rebels from the planet. Wedge Antilles, Luke Skywalker, C-3PO, and R2-D2 had all been seen on the base before the creation of Echo Base on Hoth. The Rebels stationed here were on constant alert for stormtroopers patrolling the nearby mountains.
Imperial spy Finn Darktrin infiltrated the Rebel Alliance and visited the base, but decided not to reveal its location to the Galactic Empire. The Alliance probably abandoned the base after they learned of Finn's true allegiance
