Tesla and SpaceX CEO Elon Musk attended the inauguration of President Donald Trump Monday morning ... and looked preoccupied by the ornate interior of the room.

Musk seemed fascinated by the museum-quality décor of the Capitol Rotunda, with its giant paintings and elaborately designed architecture, including on the ceilings. He shook hands with a few people, then cast his gaze around the room with wide-eyed curiosity, taking it all in.

The event was held inside the Rotunda, which holds about 600 people, after frigid temperatures forced the event normally held outdoors, inside.

Musk is joined by other tech moguls including Jeff Bezos and Mark Zuckerberg, of Amazon and Meta, respectively.

Former presidents Barack Obama, George W. Bush, and Bill Clinton were in the room ... and other notable celebs attended, including Dana White, Joe Rogan, and Jake and Logan Paul.

Elon supported Trump for president, pouring $250 million into his campaign ahead of the November election. He's been named by Trump as co-chair of the Department of Government Efficiency, or DOGE, along with entrepreneur and former Republican presidential candidate Vivek Ramaswamy.

Trump is taking office today for his non-consecutive second term as president, only the second man to do so in U.S. history.