The Boring Company, a project by Musk to build underground highways to alleviate traffic congestion, has raised $675 million in a Series C round.

The round was led by Vy Capital and Sequoia Capital. The company says it will use the funds to increase hiring across engineering, operations and production in order to build and scale Loop projects and accelerate the research and development of Prufrock, the company's next generation tunnelling machine.

In October, The Boring Company received initial approval to build a transportation system that would shuttle passengers in a network of tunnels under Las Vegas beyond its current 1.7 mile footprint that currently connects the Las Vegas Convention Center campus to a 29-mile route. The updated Vegas loop should begin this year, according to the company.

The announcement hints at other projects in the works, but the company hasn't said whether it is pursuing other projects. With increased boring speed, this type of transportation architecture can be applied to inter-city.

Improvements to Prufrock come in the form of an automated mining machine that can tunnel continuously and without humans on the ground. The Prufrock-2 can mine at 1 mile per week. The company claims that it can complete a tunnel the length of the Vegas Strip in a month.

The Prufrock 3 is designed to tunnel at seven miles per day.

In the short term, if each Prufrock-2 mines at 1 mile/week, and TBC produces 1 new Prufrock machine per month, then the company will be introducing 600 miles/year of capacity.