The wide road from the Kikyo-mon and the waterworks in parts of the outer garden runs directly to Tokyo Main Station, with it being only a short walking distance to boot. While walking down, we came across two things:
One was a competition or other kind of event with several show groups, taking place on the middle, pedestrian are. Several of the groups you can see here preparing.
The other was another sign of the ongoing Motor Show. A parade of a number of classic cars like the one in front.

The inner keep area as seen from the foundations of the donjon. The park is quite popular a recreational area. Quite understandable, it's a beautiful and amazingly tranquil place.

The Fujimi-Yagura, one of only three keeps remaining of the original eleven of Edo Castle. It took on the role of the main donjon after the latter was destroyed. And it's very unusual in that castle keeps usually were no more than two stories high, while this one has three stories.

The walls of the courtyard with a good view on the loop-holes. Useful for safely observing an enemy on the other side of the moat. And taking a shot at him.

The East Gardens of the Imperial Palace are open to the public, but not on every day. We didn't know and hit closed doors on our first visit (which is when we took the earlier photos from the Imperial Gardens), but came back on a later date. This is the eastern entrance gate, next to the Museum of the Imperial Collections. We are currently standing in the courtyard of the gate proper, looking through the inner gate.
Passing through to the left is the booth you get a plaquette from that you'll have to return upon leaving. This, together with the guards doing a headcount, serves the purpose of making sure everyone has left the park upon closing time.