Tokyo Tower is a smaller version of the Eiffel Tower. It's painted red. It costs around $12US to go to the top level.
The views are good. It is a different perspective of the city than you get from City Hall. You can see Tokyo Bay and the Rainbow Bridge from the Tower as well as the tall buildings of the Shinjuku area.
There is a small glass floor on the one level that gives you a view of the base and street. You can walk across it if you want. The base has lots of small souvenir shops and some snack shops, too. It's within walking distance of a J.R. Train station.