With its salad bars and fresh-never-frozen burgers, Wendy’s has long billed itself as a classy alternative to its fast food competitors. One of the fanciest elements of the chain could be found not in the menu, but in the architecture. Customers who frequented the burger joint in the 1980s, '90s, and early 2000s will remember the sunrooms, or solariums, that were part of so many locations. If you’ve noticed that the sunny, glass dining areas are less common in the 21st century, you’re not the only one.

According to MEL magazine, Wendy’s began phasing out its solariums beginning in 2012. Prior to that, they had been a hallmark of the company’s distinct style for decades. While many fast food chains were embellishing restaurants with colorful, plastic play equipment, Wendy’s took a more mature approach to its design. The first solariums they built in the early 1980s were meant to evoke upscale living. Sunrooms were a popular architectural feature at the time, and interest in solar technology was growing.

At Wendy’s, the warm, sunny spaces decorated with hanging plants and wood paneling invited diners to make themselves comfortable. The transparent walls also doubled as built-in advertising when passersby saw the dining room filled with happy customers. A New York Times article that reported the trend in 1985 reads, “[C]hains are gussying themselves up so that they look and act more like full-service restaurants while remaining fast-fooders. It’s something like putting a tuxedo on a hillbilly.”

This approach has since been perfected by chains like Panera Bread, but it was still fresh in the mid-1980s. In addition to influencing the aesthetic of the fast casual restaurants that began appearing in the 1990s, Wendy’s inspired other fast food companies. Solariums could be seen in chains like Arby’s, McDonald’s, and Dairy Queen around the end of the 20th century.

Today they’re nearly impossible to find in the fast food landscape, and that’s mainly due to changing trends. Solariums may be nostalgic for people who grew up in the 1980s and ‘90s, but to brands they’re dated. Many Wendy’s restaurants have been updated in recent years to have a sleek, modern look. The company is also making its locations more energy-efficient, which is another reason the solariums were retired. (They were expensive to cool in the summer and heat in the winter.) In addition to changing the design of its stores, Wendy’s has also left its salad bars, yellow packaging, and old-school logo in the past.

Even without its sunrooms, the chain has held onto its unique identity in a crowded market. You’d be hard-pressed to find chili or baked potatoes at any other fast food restaurant. Here are more facts about Wendy’s you should know.

This article was originally published on www.mentalfloss.com as Why Wendy's Quietly Got Rid of Its Elegant Sunrooms.