As reported by John here, there has been a true-to-size Gundam in Shiokaze park, Odaiba since June to promote Green Tokyo.
As I was in Tokyo this weekend, I decided to go check it out in person.
It was awesome!
Unfortunately it is being taken down at the end of August and I don't know if it is being moved elsewhere. Hopefully it'll come to Nagoya.
There are also reports that they are building a life sized Gigantor in Kobe as well.