With a little more than a month to go before the Boring Company opens its first ultra-fast transit tunnel to the public, CEO Elon Musk gave future riders a preview of what the tunnel will look like on Saturday. Musk tweeted a video of what he said was the “full length” of the tunnel, which runs underneath Los Angeles.

Musk said he walked the entire tunnel and posted a sped-up video of it over the weekend. He called the tunnel “disturbingly long,” though in actuality it stretches for less than 3 miles. The tunnel starts beneath SpaceX property in the Los Angeles suburb of Hawthorne and ends northwest of there.

The Hawthorne tunnel, which the Boring Company has always called its “test tunnel,” will hold an opening night ceremony on Dec. 10. The next day, it will offer some “free rides for the public,” Musk announced back in October. If it works, the Hawthorne tunnel could validate Boring’s signature “Loop” technology that could facilitate rapid underground transit.

The Boring Company’s idea is to put up to 16 passengers in what it calls “autonomous electric pods” that can travel at up to around 150 miles per hour throughout these tunnels. The tunnels, theoretically, will be accessible via “Loop Lifts,” or elevators that could be placed in offices or homes.

These tunnels will also accommodate single-passenger vehicles, according to Boring. The company also plans to build three other tunnels that utilize this technology.

The so-called “Dugout Loop” would transport passengers to and from Dodger Stadium in Los Angeles. According to the Boring Company website, residents of neighborhoods like Rampart Village, Los Feliz and East Hollywood would have direct access to the baseball stadium through this tunnel.

The company also made a deal with Chicago to build a tunnel between O’Hare Airport and downtown Chicago. Called the Chicago Express Loop, it would end in Chicago’s Block 37.

Musk’s company has also proposed a Loop tunnel that would run between Washington, D.C. and Baltimore. It would act as a “central artery” for a future tunnel network that also loops in New York, per Boring.