While trying to learn when the second third of the High Line will be opening (mid-may?) I came across this upcoming feature that looks cool, The Woodland Flyover:
In response to the microclimate created by adjacent buildings, which supports dense plant growth, a metal walkway lifts off from the High Line level and allows the landscape to fill in below. While an undulating terrain of moss and shade groundcover blankets the High Line bed, the Flyover carries visitors upward, into the shady canopy of a stand of sumac trees.
On a related note, check out my friend Derek's mid-story forest photos he's been taking.