When NASA sent four astronauts toward the Moon this spring, the cameras did what cameras always do at a launch. They pointed at the rocket. Artemis II was the first crew to fly around the Moon in more than 50 years, a 322-foot stack throwing fire over the Florida coast on April 1, and it earned every second of airtime it got.

But the rocket didn’t get itself to the launch pad. The machine that did is older than all four astronauts who flew the mission, weighs more than the rocket it carried, and moves so slowly you could lap it on foot without breaking a sweat. It is NASA’s Crawler-Transporter 2, and Guinness World Records lists it as the heaviest self-powered vehicle on the planet. While everyone watched the thing going up, the real engineering marvel spent the better part of a day going sideways at less than a mile an hour.

Start with the number that got it into the record books. Crawler-Transporter 2 weighs 6.65 million pounds, or about 3,106 metric tons. Guinness World Records made it official back in 2023 at a ceremony at Kennedy Space Center, handing NASA a certificate for the heaviest self-powered vehicle ever built. For scale, that is roughly the weight of 1,000 pickup trucks stacked on top of each other.