We recently reported that an exclusive report has blown the lid off of Apple’s top-secret “Project Titan” — but not many people know the details and what kind of super-secret technology they’re working on.

Apple is looking for a secure location to test a self-driving car in secret as part of this project in order to take on other competitors like Google and car companies that are also working on similar projects, according to the Guardian report.

Rumors have been flying about Project Titan for a while, but Apple has said nothing about it, and the Guardian was the first to actually apparently confirm its existence, with plans obtained that suggest it will undergo tests at a military facility under high security. But what exactly is it?

One rumor, according to AppleInsider.com, is that the company is using a BMW i3 series as the vehicle for this project. Apple will build the software that goes in it, and the vehicle will be tested on a 2,100-acre property near San Francisco that it will have to share with other companies working on their own self-driving car concepts.

In addition, Apple may be using a shell corporation — SixtyEight Research — to hide its operations. SixtyEight Research portends to be a market research company. AppleInsider reported that SixtyEight LLC imported a 1957 Fiat Multipa 600, a brand that Apple’s chief designer is known to like.

The actual facility is the Concord Naval Weapons Station, which although it is no longer a military base, it still has military guard, giving Apple total secrecy as it works on testing. The base is home to the GoMentum Station, which is where these projects are tested.

Reports indicate that several hundred workers are hard at work on Project Titan, and Apple may have been poaching executives from other companies.

And it was Apple operations chief Jeff Williams who called cars the “ultimate mobile device” back in May, which only fanned the flames of the rumors.