Somewhere in the upper floors of the old Hotel Jefferson, behind walls that went up in the 1950s, there is a ballroom that nobody touched for seven decades.

The Hotel Jefferson opened in 1904 — one day before the World’s Fair — and was immediately considered the finest hotel in St. Louis. The Democratic National Convention was held there that year, and again in 1916. A 1928 expansion added the Gold Room: a two-story jazz age ballroom with mirrored plaster walls, undulating balconies, a crystal chandelier, and a stage backed by a floating swan sculpture. Sergei Rachmaninoff performed there in 1930. Judy Garland. President Truman. The Veiled Prophet debutante dinners, annually, until they stopped.

Then the room closed. The hotel declined, became a Sheraton, then a senior residence called the Jefferson Arms. When the building was converted, someone put up walls. The Gold Room sat behind them, untouched, for the better part of a century — chandeliers still hanging, balconies still intact, the stage still waiting for someone who wasn’t coming.

Urban explorers found their way in over the years. Photographers documented it. The Preservation Research Office published photographs of the room as it sat — faded but almost entirely intact, like a party that just stopped. One former tenant told a writer he had once found his way into “a gold ballroom” and been stunned. The building’s managers didn’t advertise it.

The Hotel Jefferson is currently being restored as an AC Hotel by Marriott. The Gold Room is coming back. Whatever mysteries it kept for seventy years will soon be open to anyone who buys a drink at the bar.