After being discovered in old beta files, the abandoned Fort Zancudo bunker is now a fully explorable PC mod.

Hey kids, remember the Chiliad Mystery? After more than a decade of speculation, Grand Theft Auto V players can finally explore one of gaming's most intriguing mysteries: a hidden underground alien facility that Rockstar Games cut from the final game.

The secret bunker, buried beneath Fort Zancudo military base, is a conspiracy theorist's dream: extraterrestrial specimens suspended in tubes, a medical dissection laboratory, and military-grade containment areas.

Thanks to dedicated modders who spent months restoring the abandoned content, players can now download and explore this eerie location for themselves - but the road to achieving this is almost as interesting as the content itself.

The entire fiasco began last April when a pre-release beta version of GTA V surfaced online. Hidden within those old PlayStation 3 files, data miners found references to an underground facility connected to the infamous Mount Chiliad mystery, which, according to one former Rockstar developer, may have been a prank all along.

Specifically, the beta files contained an entire underground complex featuring three alien bodies preserved in glass tanks, a sterile medical examination room equipped for extraterrestrial autopsies, and a massive hangar area.

However, at the time, the original files were essentially broken. It had no lighting system, broken object collisions, and doors that wouldn't open, among other things. Everything in it suggested that Rockstar abandoned the content midway through development, never to revisit it again even in Grand Theft Auto Online.

That's where modder Antasurris and his team stepped in. The challenge was converting old PS3 files to work on modern PCs and rebuilding large portions of the bunker from scratch. If you're curious, the mod, Black Project: Zancudo Facility, is now available as a free download for both Grand Theft Auto V Legacy and Grand Theft Auto V Enhanced.

Despite its unfinished state, certain areas showed remarkable attention to detail, as revealed in this post on the GTA Forums. The main corridor and dissection laboratory contained far more polish than other sections, with proper textures and environmental storytelling elements.

Rockstar has a long history of cutting out content from its games. Obbe Vermeij, former Rockstar North technical lead, formerly had a blog that was essentially taken down for revealing too much about cut content.

Most recently, Trevor Philips' voice actor, Steven Ogg, confirmed that he had recorded lines for a planned DLC for GTA V that never came to fruition. It is generally understood that some content from that DLC ended up in Online.

With Grand Theft Auto 6 set to release on May 26, 2026 on the PlayStation 5 and Xbox Series S/X after roughly a decade in development, it'll be interesting to see what kind of cut content data miners will uncover.