Six years ago, SpaceX installed an above-ground tube in front of its Hawthorne headquarters, drawing excitement and intrigue from around the city about Chief Executive Elon Musk’s latest experiment.

At annual competitions, engineers and students from across the globe sought to develop and test Musk’s proposed Hyperloop transportation technology, which promised to hurl passengers through tunnels in levitating, autonomous electric pods at more than 600 mph, cutting a trip from Los Angeles to San Francisco to 35 minutes.

Today, there is no Hyperloop system in service. And after sitting idle for several years, the tube on Jack Northrop Avenue — which drew complaints about road and pedestrian access, as well as questions of its purpose — has been removed, at the city’s request.

It remains unclear whether SpaceX or Musk’s tunneling venture, Boring Co., are continuing to develop the Hyperloop technology. Bloomberg, which first reported the Hawthorne tube’s removal this week, called it “symbolic of a larger retreat” and said the Hyperloop project “has been indefinitely shelved.”