Nearly a decade ago, the billionaire said he’d build a hyperloop. Since then, he’s mostly built tunnels for Teslas and his own employees.

It's called the Music City Loop, and the project marks Musk's latest effort to bolster his budding business empire in Tennessee. His artificial intelligence startup xAI, the parent of social media platform X, is building data centers and a power plant in Memphis, on the western side of the state.