Thanks! Its good to finally take part in the discussion. I've been obsessed over all of this for way too long & I may slip into postpartum depression now that its done. Thankfully there are still some towers, a transit hub, and a fabled performing arts center to fixate on!
The grass does a lot to give visual interest to the site & I think how the designers laid it out was pretty clever. It seems quite inviting for a momentary sit, but the way they broke it up with paving and drain channels hints that you're not meant to be sunbathing or playing frisbee. Its also quite effective at subtly corralling visitors towards the pools.
The landscape design of the memorial is kind of genius. the whole thing has a subtle accordion pitch to it so that water drains into the irrigation channels and I learned today that each tree has sensors embedded in the soil! If it's your thing, the landscape architect's site is an interesting read:
http://www.pwpla.com/national-911-memorial
For me the next puzzle piece is the museum roof and how they're going to make the stairwell that pops out the top look good...