Emoji are going to be some of the most recognizable icons of the 21st century, says architect Changiz Tehrani, which is why he decided to cast 22 of them in concrete and use them as decoration for a building in the Dutch city of Amersfoort.

“In classical architecture they used heads of the king or whatever, and they put that on the façade,” Tehrani told The Verge. “So we were thinking, what can we use as an ornament so when you look at this building in 10 or 20 years you can say ‘hey this is from that year!’” The answer was obvious: emoji.

The end effect is actually pretty subtle. The building is built around the lines of a grid, with pillars of brick, beams of white concrete, and decorative circles at the intersections. The emoji only appear one one side of the building, which faces into a town square constructed around a 150-year-old oak. The building itself is mixed-use, with shops on the ground floor and flats above; while the rest of the square is home to a library, a theater, and a school — another reason for using emoji.

“There’s all these young people there, and emoji is a thing of now,” says Tehrani, who works for the Dutch firm Attika Architekten. “The students sit in the square and have lunch and they take pictures. They like it. And with our architecture we always like to put in small details that makes the project a little bit more than a boring building.”

The design for each emoji was taken from the template used by WhatsApp, and converted by Attika into a 3D model. These were then sent to the building company involved in the project, which created molds for the emoji and cast them in concrete. Only faces were chosen as they were the most expressive and recognizable emoji.

Construction on the building finished in 2015, but commercial occupation only began last summer, with official pictures published last month. The reaction has been uniformly positive, says Tehrani, though he admits he never asked older residents of Amersfoort what they thought of the construction. “I don’t know if older people recognize the emoji,” he says. “But if you have a smartphone, you will have seen them.”

Critics might say that using emoji in architecture is a gimmick that will soon show its age, but Tehrani says that’s precisely why the project is interesting. “If you look at history, people always think ‘Oh this is timeless,’ or ‘This will stay forever,’ and they’re always wrong.” Better, he says, to accept that aiming for architectural immortality is impossible, and have fun embracing what’s truly contemporary. “It’s like with Facebook. Facebook used to be cool and now it’s just for older people. So maybe we won’t use emoji in 10 years — that’s fine. It’s still from our time.”