Finally made it to the Imperial East Gardens on the 3rd attempt. Walked over from Tokyo station to the gardens. They are really nice but quite reserved.
Afterwards we gave in an bought subway cards as the train stations are not always near the places we wanted to visit. 1000 Yen for the Tokyo metro excluding the Toie lines (which is a separate subway system because Tokyo is so massive it needs more than one underground system!).
After the gardens we went for a walk around visiting the Mori are museum. Grabbing a great view of Tokyo at night and eating some rice balls.