Free viewing platform in Shinjuku; you can see night view of Tokyo

There is a free viewing platform at Tokyo Metropolitan Government in Shinjuku city. I think this spot is pretty good because of the nice view in spite of free charge.
The viewing platform is on 45th floor, so you can look over the landscape of Tokyo city, and even Mt. Fuji if weather permits.

Souvenir shop and cafe are also there.

I recommend you visit there. You can get there in about 10 minutes by foot from Shinjuku station.