As I entered the address "1 Hacker Way" into my hire-car's GPS-system, I half-expected to arrive at a dark cubbyhole full of furtive data-espionagists. The reality was slightly different. The terracotta-coloured building at my destination had all the ambience of a well-to-do retirement home, encircled by roundabouts and pampas grass. It was Swindon with palm trees.

You'd never guess that this was the global HQ of Facebook, the social media site that has revolutionised the personal and business lives of its 1.2 billion users over the past decade. It was midday on a Friday, but the only activity at its Menlo Park nerve-centre was a bored-looking gardener clearing leaves and tinkling lawn-sprinklers.

However, peering into the Facebook reception, it was like glimpsing Heaven's pearly gates – only with added fresh, barista-brewed coffee. Through the glass doors, I could see happy, healthy twentysomethings sashaying down a tree-lined boulevard, clutching gratis lunches and plastic folders, slinking off to slope-roofed huts housing goodness-knows-what fun.

It's been 10 years since a teenaged Mark Zuckerberg launched Facebook with his Harvard roommates. And over the past decade, Facebook, along with Silicon Valley neighbours Google and Apple, has defined our age. Even so, few tourists bother to visit this geographically nebulous region in the southern San Francisco Bay Area. The closest I could get to the sunny utopia on the other side was logging on to Facebook for the world's ultimate "check-in" status. Even that went awry when Wi-Fi faltered. Tech heaven? Pah!

Home base: Facebook HQ Home base: Facebook HQ Next on my hit-list was the fabled Googleplex, a 20-minute drive away at 1600 Amphitheatre Parkway. The first sign that I was in Google-ville was when a blur of people whizzed past on bikes. A little further on, these rainbow-hued two-wheelers were everywhere, in the bright colours of the company's logo. Electric cars purred past me. Five people grappled with a circular ConferenceBike and a man strode past wearing a shiny, purple foil jacket. He was possibly a "20 per center" – staff encouraged by Google to spend one-fifth of their time experimenting with new ideas.

While strolling around the Google campus and posing for photos is allowed, entering the hallowed sanctum is not. I desperately wanted to find the Google X laboratory where engineers work on such secret projects as talking fridges and (allegedly) lifts to space. However, all I spied were workers heads-down in an open-plan office, and signs promoting free massages and haircuts.

Facebook and Google aren't the only Silicon Valley tech sites. A drive along the Santa Clara Valley revealed offices for eBay, Microsoft, Yahoo!, the Apple HQ at 1 Infinite Loop, as well as the HP Garage. This unassuming shed at 367 Addison Avenue was where William Hewlett and David Packard developed HP's first product – an audio oscillator – in 1938, giving birth to Silicon Valley as we now know it. Today, it's a private museum and designated historical landmark with a small plaque outside.

The valley is also home to the Computer History Museum, which explains the evolution of computers, from the abacus to 1940s house-sized super-computers through to today's state-of-the-art tablets. It also presents the grand follies of the Computer Age – the 1960s Honeywell kitchen-computer intended for housewives (tagline: "If only she can cook as well as Honeywell can compute"). Or the precursor to Google Glass: the 1968 Sword of Damocles "virtual reality" headwear. Elsewhere, there were retro Speak&Spells, East German home computers from the 1980s, and an interactive section where teenagers play Pac-Man and PONG (the world's first commercial computer game). There's even a space dedicated to Teletext.

Visitors at the Computer History Museum Visitors at the Computer History Museum The Social Network movie portrayed Silicon Valley as a sun-drenched party-zone. However, the reality of visiting bars here is eavesdropping on talented techies' conversations. In 2010, at Redwood City's German beer garden, Gourmet Haus Stadt, an Apple employee lost an iPhone 4 prototype, which later ended up on tech blog Gizmodo. The bar was empty on my visit, but there was a bizarre gift shop, hawking Teutonic TV mags and packet soups. I fared better at Martins West gastropub, dining on haggis-on-a-stick and a veal tongue butty while listening to nerds pitching ideas about Android APIs.

Nearby Palo Alto contains another web 2.0 pilgrimage site – Steve Jobs's former mansion at 2101 Waverley Street, which resembles an English country pile, with bus-loads of tourists arriving to pay homage to the great man. Palo Alto is exactly the kind of streamlined Arcadia you could imagine Jobs inventing: functional, easy-to-navigate, and disconcertingly sterile, with convertible Mercs parked outside upscale restaurants, such as MacArthur Park.

Despite the campus of Stanford University being on the doorstep, there was no sense of a typical Friday evening in a student city. Still, perhaps they were all eye-deep in computer programs, plotting the next phase of the tech revolution.