Putting up walls can be a good thing. That is, if you’re talking about retaining wall ideas in your landscape design. “At the basic level, a retaining wall is a structure that holds or retains soil behind it,” explains Joe Raboine, director of Belgard Residential Hardscapes, an outdoor hardscapes company. “Though retaining walls are most commonly used to create a functional area out of a sloped terrain, they do serve other functions.” You might think that retaining wall ideas are all about function—after all, retaining walls prevent soil erosion and reduce the risk of flooding—but they are not all utility; these structures can enhance an outdoor space by creating levels,…