Every morning she works, Rosemarie Croll heads down into the singular space of the Buffalo Bayou Park Cistern to sweep and prepare for the day’s visitors, alone and dwarfed by the cavernous cement structure. A couple of times, she has found toads in the walkway and tried to coax them to safety with her voice. They eventually made their way up the stairs and out the door, in search of Houston’s endless buffet of mosquitoes.

And she sings.

Anyone who has taken a history tour of the Cistern with her will tell you that Croll is a unique musical talent, even in a city that produced Beyoncé and the Suffers. These informative tours underground often end in song. Some of the tour guides will sing pop or folk tunes, such as “The Rains of Castamere” from Game of Thrones, but Croll specializes in compositions she writes herself specifically for the space that inspires her and changed her life.

“I truly believe that in the future this will have some kind of historic status,” she says, gesturing to the softly lit columns on an afternoon in early January. “All the special places people visit over Planet Earth absorb positive energy. I am only hoping that the Cistern will have that one day.”

Croll was having a rough time before she came to work at the Cistern. When she took the job part-time on a whim in 2016, she had been out of work for two years. Before that, she was a technical editor for a large computer company, a remote role that kept her home and isolated from people.

“I had a couple of virtual colleagues, but that was it,” she says. “Otherwise, I was alone on my couch for nine years.”

Something about the Cistern drew her in immediately. She’s far from the first. Built in 1926 as a subterranean drinking water reservoir, the Cistern is a marvel of modern architecture. The Basilica Cistern in Istanbul, Turkey, inspired its design, giving it a cathedral-like appearance.

The cement columns appear to stretch hundreds of feet into the depths thanks to a trick of the light and the still shallow water, but even that illusion is outdone by the echo. Croll demonstrates it by inviting audiences to shout and wait for their words to wander the Cistern for 15 to 20 seconds.

“I never know who I’m going to get,” Croll says. “Every yell is different. Sometimes they sound like angels.”

By the end of her first year at the Cistern, Croll was singing to show off the Cistern’s echo. At first it was the likes of “Down in the Valley” and “God Bless America.” However, Croll was a vocalist with an 18-piece jazz band in her youth, and she even composed her own songs and released an album called Spotty Sprinkles of Love in 2001. The Cistern made her want to write again.

“I can only create when I’m inspired,” she says. “When it’s not the right moment, it’s painful. The heart can only express when it’s the right moment.”

That moment came during the first winter of COVID. She was driving to work when she began composing her specialty songs for the Cistern. By January 2021, she was performing them regularly.

The result is a small suite of tunes that audiences can hear only by taking the tour. One of them, “The Facts about the Cistern Song,” is a recap of the Cistern’s measurements and history—it doesn’t rhyme much but does cram a lot of information into a few melodic minutes. But it’s her tributes to the space itself that really stand out. Framed almost as hymns, they are deep compositions about the power of water, sound, strength, and the sacredness of places people love.

Another song, “The Colored Lights in the Cistern Temple,” goes: “The shallow water on the bottom turns more darkness into light.”

“So much positive feedback,” says Karen Farber, vice president of external affairs for the Buffalo Bayou Partnership. “It’s all over the internet. People say they’re amazed by the tour guides, and they always mention the singing.”

By far, Croll’s most moving performance came in September 2022. Queen Máxima of the Netherlands visited Houston as part of a national tour and wanted to see the space. Croll was being granted the chance to perform for royalty, albeit in an underground industrial structure as opposed to a palace in The Hague.

“I never anticipated I would do anything like it in my life,” Croll says. “I almost fainted when she left. I was so overcome.”

Croll had to keep the visit secret for six months for security reasons. On the day Queen Máxima arrived, she shook Croll’s hand and let the tour guide lead her into the structure flanked by Dutch press. Croll gave her presentation about the history and ended with a rendition of her song “The Cistern Is.” Queen Máxima shed a tear, deeply moved by the singing.

“Then I realized I should have been able to sing it in Dutch for her,” Croll says. “I set my mind on learning other languages to sing the song in. Her Majesty inspired me to be a better person.”

While Croll has yet to master the Dutch version, she has spent the past year performing the song in nine other languages. Fellow tour guide Lou Alejandre of the band La Prave helped her with Spanish, while an Arabic translation was provided by Lutfi Mized, a visitor who volunteered. She’s hoping to expand to Hebrew and Russian to accommodate more international visitors.

“I think it’s important people hear that beautiful echo in their own language,” she says. “Each language, even though it’s the same melody, somehow sounds different because of the way language works.”

That day in January, Croll sang in Spanish in honor of a visitor from Spain. He was the guest of Marcia Smith, a retired teacher from the Heights who had always wanted to see the Cistern and used the friend’s visit as an opportunity to go.

“What a wonderful way to show the acoustics in that building,” Smith said. “It was weird at first, then we admired her passion for her job. We felt it come through with her work. It was just amazing how not only the sound but the view could keep going. It was like infinity in there.”

Since opening to the public in 2016 after being repurposed by the Buffalo Bayou Partnership, many musical acts have played in the space. Sound baths for meditation happen weekly, and the echo makes many installation artists want to experiment.

But it’s Croll who has the deeper work down there. Her love of the Cistern is sincere and reverential, and her songs to it are as unique as the space itself. She is a choir of one for something strange and wonderful underground.