It is a giant, orange, flower-shaped structure that is partially buried in the sand. It is located behind the buildings of Bikini Bottom. Its design matches the flower clouds that float above the city.
It was one of the original locations that Stephen Hillenburg designed for the show in 1997. In the first concept map of Bikini Bottom, the flower arch was specifically labeled along with nine other locations. It was the only one that did not end up becoming an important setting in the series.
The flower arch is never visited or mentioned directly. It occasionally appears in wide shots of Bikini Bottom, such as in "Pizza Delivery," "Nature Pants," and "Suds." It also appears in the "Pizza Delivery" segment of the book Krusty Krab Adventures. In the book SpongeBob NaturePants, it had the some role as the episode. In the video game Revenge of the Flying Dutchman and the special "Square Roots: The Story of SpongeBob SquarePants," the arch can be seen in Stephen Hillenburg's concept artwork.