The era of Chelsea mega-galleries has arrived.

Last Thursday night, Pace Gallery opened its giant new headquarters on West 25th Street, eight stories of galleries, art-filled offices, private terraces and party spaces that cost more than $100 million to build.

The opening party drew several hundred well-heeled collectors, museum directors, artists and other art world insiders, culminating in a performance by the Who on the gallery’s sixth-floor sculpture terrace.

“We have remained relevant for 60 years, and so have they,” Arne Glimcher, who founded the gallery in 1960, said about the choice of entertainment. He is passing the baton — without quite releasing his grip — to his son Marc Glimcher. “There isn’t that much that was cool in the ’60s and is still cool now, which is still going strong.”

Blending with the neighborhood’s corporate-riche style, the new building overlooks the High Line and offers views of greige luxury apartments to the south and Hudson Yards skyscrapers to the north. It will soon by joined by mega-galleries by David Zwirner, Hauser & Wirth and Larry Gagosian.