Visitors to the National Building Museum’s The Beach became impromptu wedding guests this morning. Expecting to walk into an empty, stark white scene, the first Beach-goers of the day stumbled upon a red-clad couple exchanging their vows.

The museum opened their doors a little early for the couple and their 15 guests to begin the ceremony, which was organized by the pop-up wedding company Pop! Wed Co. About halfway through, the exhibit opened to the public and The Beach began to fill with people. “Everyone stood behind the couple, and they all applauded afterward,” said Pop! Wed’s Steven Gaudaen, who officiated the ceremony. “It was a really nice moment for everyone.”

An Instagram favorite, The Beach has been the scene for several couples’ engagement photos, but it is the first wedding as far as the museum knows.

One of the company’s photographers had visited the exhibition a few weeks before and thought it would make for a fun place for a pop-up ceremony. They’ve done other museum weddings, including one at the American Art Gallery and another at the Natural History Museum (where security actually kicked them out), in addition to a litany of other unconventional spaces. When Pop! Wed proposed The Beach to the couple, they fell in love with the idea, Gaudaen says. After the ceremony, they took some photos and headed out for a family lunch.