Installation has finally begun on Jeff Bezos’ 10,000-year clock, a project that the Amazon CEO has invested $42 million in (along with a hollowed-out mountain in Texas that Bezos intends for a Blue Origin spaceport), with the goal of building a mechanical clock that will run for 10 millennia.

The actual idea for the clock comes from Danny Hillis, who originally proposed a 10,000-year clock in 1995 in Wired as a way to think about the long-term future of humanity and the planet. That idea grew into the Clock of the Long Now, a project by the Long Now Foundation, which Hillis went on to co-found to build an actual, working version of the proposed clock.

Installation has begun—500 ft tall, all mechanical, powered by day/night thermal cycles, synchronized at solar noon, a symbol for long-term thinking—the #10000YearClock is coming together thx to the genius of Danny Hillis, Zander Rose & the whole Clock team! Enjoy the video. pic.twitter.com/FYIyaUIbdJ — Jeff Bezos (@JeffBezos) February 20, 2018

The group built a couple of prototypes, but Bezos’ clock — which Hillis is designing — will be the first to function on a full scale. The team has spent the last few years machining parts for the clock and drilling through the mountain to store the components. Bezos announced today in a tweet that installation of the machinery has begun on the 500-foot-tall mechanism.

According to the website for Bezos’ 10,000-year clock, visitors will (in theory) be able to view the finished timepiece, although the site notes that it’ll be a rough trip. “The nearest airport is several hours away by car” and a rugged foot trail that rises almost 2,000 feet above the valley floor.

Fortunately, if the clock runs for as long as it claims, you’ll have plenty of time to plan your trip.