MENLO PARK, California — Dressed smartly in a dark pullover and tan chinos, a black backpack slung over his shoulder as he strolls across the social networking giant's sprawling micro-society of a corporate campus on a sunny Wednesday afternoon, Harrison Barnes looks almost like any other 20-something Facebook employee.

Then you remember a few things that set Barnes apart: he's 6'8", he was the seventh overall pick in the 2012 NBA Draft, he plays for the Golden State Warriors and he's one of the NBA's young stars.

See also: A YouTube Legend Battles for His Basketball Future

The 22-year-old Barnes has had a packed summer. He went to Brazil to take in the World Cup. He spent a week in Las Vegas as part of USA Basketball's national-team training camp. Grinding workouts, meanwhile, are a constant.

But sandwiched between workouts this week, Barnes has added another item to his summer list: making the 40-minute drive from Oakland, where he lives, to Facebook's Menlo Park headquarters like any other Silicon Valley grunt.

Facebook calls him an "extern," not an intern. Barnes isn't getting paid, and he's not taking a hungry college student's spot. But he's meeting, working with and shadowing Facebook employees this week, giving — and receiving — knowledge in the process. His presence in Menlo Park is twofold.

Harrison Barnes takes it to the hoop for the Golden State Warriors. Image: Mark J. Terrill/Associated Press

First, as one of pro sports' more active and savvy Facebook users, he's there to learn even more about the platform. Second, he's there to provide Facebook's development teams with feedback it can't get from anyone but the high-profile athletes and celebrities who use their products, particularly the recently-launched Mentions app.

Athletes like Barnes are a valuable asset as the company looks to continue building momentum in the sports world. While Barnes is the first to take part in this particular externship program, it's one Facebook reps say the company hopes to continue with other athletes in the future.

"Being in the NBA and able to connect with fans through social experiences is great," Barnes says, sprawled over an undersized chair in a brightly lit meeting room where he's about to conduct a Q&A with fans on Facebook. (He'll reveal a taste for Biggie over Tupac, say the Raptors are his favorite NBA 2K team and pledge to try Filipino food before the season starts, among other nuggets.)

"But then to come here and connect with the people who make these tools and learn how to use them more effectively and also talk about how they can be enhanced is even better," he adds.

Facebook plans to put his feedback to good use. Allison Swope, product manager for the Mentions app, says Barnes' ideas and insights as a high-profile user this week have been so good she can't share them — her team actually plans to develop a couple into new features on the platform.

Harrison Barnes answers fan questions using Facebook Mentions while at Facebook HQ. Image: Mashable/Sam Laird

Facebook would be hard-pressed to find a better fit than Barnes to pilot what it hopes will be an ongoing series of mini-residencies with major athletes. The Warriors are among the NBA's most digitally savvy teams and Barnes himself stands out among the Warriors players.

In recent months he's held numerous Q-and-A sessions with fans, put on creative contests, showed off meeting a comedy legend, posted a heart-warming video from a fan and helped one Make-A-Wish kid's dream come true. Barnes' tech and marketing savvy goes back years, though; he committed in 2010 to play college ball at North Carolina via a televised Skype call.

Facebook, meanwhile, wants to build on some growing momentum in the sports space. The recent World Cup, for example, was its most talked-about event of all time. And when American soccer legend Landon Donovan announced his retirement this Thursday, he did so on Facebook.

Put Barnes social savvy and Facebook's rising sports profile together and you get an unpaid millionaire extern in tan chinos who's probably the tallest person on Facebook's campus this week — and most certainly the only one who can reverse-dunk like this:

Barnes, for his part, looks to be enjoying the taste of a life much different from his own. His Facebook posts this week note the perks of working at a place full of free on-campus eateries. On Tuesday, he used his fans to crowd-source questions before meeting with a Facebook engineering team.

He also seems to have developed a special affinity for the "gravity room," an optical-illusion set up in one Facebook building so visitors can take trippy Instagram photos. "Oh, you have to see the gravity room," he says at one point with a genuine enthusiasm belying his young age. And so it is that we end up taking a series of topsy-turvy photos.

Image: Mashable/Sam Laird

But Barnes has long had a businessman's mind. “The longer you stay in college the better a brand you build,” he told The Atlantic in 2012 as part of his reasoning for returning to Carolina for his sophomore year.

So in many ways it's not all that surprising to see him at Facebook this week, teaching and being taught, building connections and taking prime advantage of the Warriors' Bay Area location. It all leads to an obvious question: Is Barnes eyeing a move into online entrepreneurship or investment someday down the line?

"There's going to be a time when the ball stops bouncing and you have to move on to something different, whatever that is," he says, not revealing too much. "But I just know I've loved being involved with technology and social stuff these past two years."

While that's not an ironclad answer by any means, there is one thing Barnes is sure about.

"I don't know if taking on Facebook is going to be a good career move for me," he says with a laugh. "I think I'm going to let them do that."

For now, at least, Harrison Barnes will stick to basketball.