I can clearly remember two pieces.
The first one is a throne, much larger than normal human size. It sits at the base of a hill, amongst a huge old-growth tree-fern forest. It is made of rough timber and bronzed metal. I had to clamber up into it to sit. I feel it implies that we are insignificant in comparison to this forest and that we need it.
A snake mosaic stretches part of the track to Cape Pillar; its head and its tail is separated by colorful mosaic tiles for at least a kilometer. I love how this piece is incorporated into the track; adding instead of subtracting.