Here's something you might not know: Jeff Bezos – the founder of Amazon and rocket company Blue Origin – owns a mountain. Yep, an entire mountain in Texas.

Not only that, but the (sometimes) richest person on the planet has figured out the perfect thing to store inside his mountain: a giant mechanical clock designed to last 10,000 years. Hey, you don't get that rich without thinking outside the box a little, right?

Seriously though, what's the deal with this insane-sounding clock project, said to cost a whopping US$42 million?

It's actually the brainchild of inventor and scientist Danny Hillis, who came up with the concept decades ago, envisaging a clock that would truly stand the test of time – ticking only once per year, with a 'century hand' moving once per century, and keeping perfect time for the next 10 millennia.

As you can see, absolutely nothing about this tinkering project is small. It's even a little scary in its scope.

"Over the lifetime of this clock, the United States won't exist," Bezos explained to Wired back in 2011.

"Whole civilisations will rise and fall. New systems of government will be invented. You can't imagine the world – no one can – that we're trying to get this clock to pass through."

That was several years ago, by which point Bezos had been working with Hillis on the 10,000 year clock for some time, and the inventors – who call themselves The Long Now Foundation – said the final design and engineering of their time-travelling timepiece was almost complete.

Then, things went pretty quiet on the clock front, until this week, when Bezos tweeted an important update on the project, sharing a video on the project and confirming installation of the 152-metre-tall (500 ft) machine is underway inside the Sierra Diablo mountain range site.

At this point we don't know for sure when the 10,000 year clock will be completed, but the Long Now Foundation has previously explained the clock will be open to the public when it's finished – meaning, if you visit at just the right time, you'll hear the clock chime… exactly once every 1,000 years.

While some have criticised Bezos for throwing his fortune away on a "vanity project", others are more sympathetic to the symbolic value of what the clock could – and should – represent.

"It doesn't have a practical purpose, per se, and it certainly won't make money," Fortune's Anne Vandermey wrote in 2013.

"It's more of a conceptual art piece designed to encourage people to be good stewards of humanity's distant future."

If that's what this mechanical marvel truly is, there are worse things to spend your millions on. After all, we haven't exactly been the greatest stewards of humanity's destiny so far, have we?

And even if you're not down with the clock, ask yourself this: does a Tesla Roadster sent into orbit make all that much more sense?