It's a grand gesture on the scale of Ozymandias - although somewhat less egotistical - a clock designed to keep time for ten thousand years.
Amazon founder Jeff Bezos is helping to build the 200-foot-tall clock in a mountain cave on land that he owns in West Texas. It ticks once a year, has a century hand which moves forwards once every hundred years - and a cuckoo which pops out for the millenium.
A chime generator creates a different bell ringing sequence each day for 10,000 years.
"As I see it, humans are now technologically advanced enough that we can create not only extraordinary wonders but also civilization-scale problems," says Bezos. "We're likely to need more long-term thinking."
After 20 years' work by Danny Hillis, construction is now well underway, and Bezos has launched a website showing its progress. The final design and engineering is nearly complete, and fabrication of the full-size clock parts has begun.
Five room-sized anniversary chambers carved out from the mountain will celebrate the first, tenth, hundredth, thousandth and ten thousandth anniversaries.
The first is a special orrery which includes all of humanity's interplanetary probes, as well as the planets and moon. This will spring into action once a year on a pre-determined date.
Bezos says the team isn't planning to fill the 100, 1,000, and 10,000 year anniversary chambers, but will leave them to future generations.
"We do intend to build the animation for the 10 year anniversary chamber, but haven't decided what it will be yet," he says. "If you have an interesting idea for the 10 year anniversary chamber, please feel free to email it to email@example.com, and we'll add it to the mix of ideas."
People will be able to visit the clock when it's completed - although it won't be easy, as it's a long hike from the nearest road. No doubt any future aliens wanting to take a look at our imposing but primitive artefacts will make alternative arrangements.