This retaining wall is located at Tanner Springs in the Pearl District of Portland OR.  As part of an urban park it was also designed to deter skateboarders while keeping with a contemporary style.  Materials: pre-cast concrete, steel fins.  Dimensions: 2' high x 10"wide, and runs the length of the park.  The pre-cast concrete is suited to with stand the elements and should require little if any maintenance, it works well as a retaining wall and is comfortable enough to sit on for a short break.