The south leg of the Gateway Arch. Go ahead and touch it! Feel the smootness of the stainless steel and find the welds between the sections. The sections were constructed as triangles, then shipped to St. Louis where the triangular pieces were welded together. The triangular pieces become smaller and smaller as the leg rises into the air. Look up as the leg curves away and notice how the view changes as you move around the side to another part of the triangle. 

Please respect the historic fabic of the Gateway Arch. Touch it! Take a selfie! But leave no mark!