A giant Amazon locker was spotted in the middle of San Francisco's Justin Herman Plaza but still holds a mystery within.

Amazon.com, the biggest online retailer, is building hype for its mysterious event to be conducted Friday, by placing a giant orange box in the middle of San Francisco's Justin Herman Plaza. What lies within is still a mystery but the retailer has a history of secretive teasers prior to launching new projects. The huge orange color locker in front of the city's iconic Ferry building has Amazon's logo on it and bears a name "Giant" on it.

The big rectangular box has sufficient room to hold a car, like the one it used to deliver a Nissan Versa earlier this year. But sources reveal the new Amazon locker is linked to an event planned for Friday, according to Wall Street Journal.

"I can be vague, but I'm not going to lie to you," an Amazon employee told WSJ, keeping the specifics under wraps.

The Amazon Giant locker features a massive door on one of the sides, which has a LCD screen, a keypad and a ticket scanner. The locker bears resemblance to the existing Amazon lockers that are located across many US cities. These lockers, which are comparatively smaller, are placed inside stores such as 7-Eleven and Ace Hardware, for people to pick up their packages outdoors. Customers receive a code that unlocks one of the drawers to collect the ordered package.

The new giant locker, however, remains a mystery but WSJ reports that Amazon will use this new marketing technique for select customers to claim prizes.

Several media reports predict the new behemoth might unleash a new way for people to pick up their packages. Amazon was previously reported to be testing aerial drones to drop off packages to people's location, an answer to speedy and efficient delivery. If the new event has something to do with enhancing delivery system, Amazon will be going ahead of its chief rivals, Google and Uber that have recently announced new services, Google Shopping Express and Rush, respectively.