Elon Musk once planned a lavish glass house for himself near Tesla headquarters in Austin, Texas, worth millions of dollars which prompted an internal investigation by the electric carmaker’s board over alleged improprieties.

According to the Wall Street Journal, Tesla planned “Project 42” last year which called for a dramatic and unusual glass-walled building for Musk to come up near the automaker’s headquarters in Texas.

The secret project included renderings of a glass box with residential features, such as bedrooms, bathrooms, and a kitchen, the report claimed, citing sources.

The project reportedly triggered an internal probe over “possible improprieties”, over concerns that Musk might be using company funds to build the house.

The secret project was described as a house for the Tesla CEO that would be located near the company’s Austin-area Gigafactory.

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There was a waterfall incorporated into the structure’s surrounding landscape in addition to a futuristic pickup truck.

The concepts for the house included either a “twisted hexagon” or a glass cube reminiscent of Apple’s 5th Avenue store.

Musk or Tesla did not immediately respond to the report.

The results of the investigation “couldn’t be learned” and it’s unclear whether the glass was ever delivered. The status of Project 42 is also unknown, according to the report.

Musk recently disclosed he lives in a tiny $50,000 rented home in Boca Chica/Starbase, near Space X’s facility.

“My primary home is literally a $50k house in Boca Chica/Starbase that I rent from SpaceX. It’s kinda awesome though,” he had tweeted.

“Only house I own is the event house in the Bay Area. If I sold it, the house would see less use, unless bought by a big family, which might happen someday,” said the tech billionaire.