Including the gardens, the whole site covers just over 7 square kilometers, but it is considered the most expensive square kilometer in the world. Actually, it is said that during Japan's bubble economy (1986-1991), the palace grounds were estimated to be worth more than all the real estate in California...
The only structure clearly visible from outside is the Fujimi-yagura tower, here right in the middle of this photo. It is a three-storied watchtower 14.5m tall, rebuilt in 1659, one of the oldest buildings of the palace. It was damaged by the Great Kanto Earthquake, but it was rebuilt using original material.
Travel Tips: Besides the East Gardens, which are opened for the public throughout the year (details), the palace interior is opened only two days per year, on December 23rd - the Emperor's Birthday (how to visit details) and on January 2nd, for the New Year Greeting (how to visit details).
EXIF info:
Nikon D90
Lens: VR 18-55mm F/3.5-5.6G
Focal Length: 55mm
Aperture: F/7.1
Shutter Speed: 1/640s
ISO Sensitivity: ISO 200