In the middle of Facebook's Menlo Park campus there's an open courtyard with the word "Hack" written in enormous letters. This area is known as Hacker Square.
Above "Hack" are nine large, thick, gray stripes.
To the naked eye, the stripes are inconspicuous. But to those who know, especially early Facebook employees, these stripes serve as a monument to the company's original spirit of "move fast and break things." They're a memorial to events that transpired in the summer of 2007.
At the time, Facebook was still a small company with no more than 300 people, and its headquarters was a trio of buildings in downtown Palo Alto, according to three former Facebook employees who spoke with CNBC.
The company operated out of 156 and 154 University Ave., but Facebook's cafeteria sat a block away at 164 Hamilton Ave.
The two buildings are separated by a three-minute walk, but Facebook employees could shorten the distance by cutting through a tiny alleyway perpendicular to Hamilton Avenue that was directly across the street from the cafeteria. To cross, employees had to walk to either end of the block or risk a jaywalking ticket because there was no crosswalk connecting the alleyway and the cafeteria.
At least there wasn't one until Facebook held an overnight hackathon during the summer of 2007.
During these hackathons, Facebook employees would bring to life the ideas they'd kept in the back of their minds but hadn't yet had a chance to execute. Usually the nights resulted in new software features for the company's website, but the aftermath of this particular hackathon was more tangible.
The following day, there was suddenly a crosswalk connecting the alleyway and the Facebook cafeteria.
For the most part, the hack went unnoticed — the crosswalk was so convincing, people actually started using it. The white stripes had been spray painted in measurement drawn to city specifications.
It wasn't until that afternoon that the authorities finally noticed. A Palo Alto police officer riding on a bicycle stopped, took his helmet off and put it under his arm and stared at the crosswalk. Finally he slapped his forehead, realizing the crosswalk didn't belong there, according to one former Facebook employee who witnessed the event.
The officer questioned Facebook staffers about the crosswalk, asking them if they knew who had painted it. It wasn't until this moment that most of the company began to realize what had been done.
People laughed, but it wasn't cool, another former employee told CNBC. The crosswalk was disrespectful to the city of Palo Alto, and Facebook did not want to disrespect the local government since it needed to be on good terms with the city, that employee said.
Over the next few days, the city erased the crosswalk by sandblasting and paving over it, leaving a darker shade of black on the road where the white stripes had been, the former Facebook employees said.
The city may have removed the crosswalk from its road, but former Facebook employees still talk about it.
"'Somebody' painted a cross walk in the middle of Hamilton Ave. so it'd be easier to get to lunch in Building 164. Classic," wrote a member of the "Facebook Archivist" Facebook group, where former employees post about their memories and experiences working at the social network.
The gray stripes at Hacker Square are the most prominent reminder.
If you ever been to Facebook's campus, you may have seen or walked on the stripes without noticing them. They sit just south of Facebook's Building 14 and Building 16. They are large enough to be visible from the satellite imagery of Google Maps, and you can clearly spot them if you do an image search of "Facebook Hacker Square."
The story of the crosswalk is often told to Facebook employees during new-hire orientations, according to the former Facebook employees, to give them a sense of the company's original culture.
That culture can be summed up in the phrase: "ask for forgiveness, not permission," one of the former employees said.
Facebook declined to comment.