The Tesla and SpaceX CEO famously told the world about his super-fast, inter-city, train-in-a-tube concept, Hyperloop—then said that other people should build it. Fair enough: he is a busy guy. But he’s now decided to build the thing himself. The news was hinted at when Musk announced a "verbal government approval" for an underground Hyperloop from New York City to Washington D.C.—and Bloomberg report last week added to the buzz—but it was only confirmed for the first time today by Wired.

Construction of the Hyperloop will be part of Musk's side project, the Boring Company. Its premise is that a "large network of tunnels many levels deep would fix congestion in any city, no matter how large it grew." There are some problems with the idea, but no matter: the company has already been digging its own tunnels in Los Angeles.

Speaking to Wired, a spokesperson from the Boring Company has explained that the firm plans to build different types of transportation systems in those tunnels. Some will be "standard pressurized tunnels with electric skates going 125+ mph," while others will "use pressurized pods in a depressurized tunnel to allow speeds up to approximately 600+ mph (aka Hyperloop)."

The news comes at a time when Hyperloop is starting to look a little less like a crushing disappointment and more like a technology that could, one day at least, work. Last week, Hyperloop One managed to fire its first pod through a low-pressure tube on mag-lev, reaching 192 mph in five seconds. Still, Musk’s vision of a Hyperloop running in underground tunnels is perhaps an even more ambitious goal than firing them through overground tubes, certainly from a city planning perspective.

Still, this is the man that was faced with incredulity when he vowed to recycle rocket boosters, then went ahead and made the whole thing look like child’s play. So his decision to build an underground Hyperloop will certainly buoy the nascent industry surrounding the peculiar form of transport, as many people will assume he can make a go of it. Whether he can or not? Keep your eyes on those tunnels.