Roppongi Hills is definitely worth a visit at least to look at the architecture/construction. I was very dissapointed in the shopping, nothing but over priced boutique style stores though there are some good restaurants. I had some great sushi there, though it cost my husband and I $100 for lunch.
Roppongi Hills. Yes, here is a link
Amazing place, worth a visit.
My husband worked on the Mori Tower (the big building in the middle) and told me that 3 construction workers lost their lives during the construction of that building.
That place is like a maze we never did figure out where exactly we were and always ended up taking the long way to get anywhere
I recommend going by car just so you can see their incredible advanced car parking system. I felt like I was transplanted 50 years in the future, it was the most incredible thing I had ever seen and I have seen some really cool parking in Japan before!