You won't see much of the actual palace. (An application and reservation are necessary for a tour.) It's closed to the public (except on New Year's Day and the Emperor's Birthday on Dec 23), but parts of the exterior can be viewed from the Nijubashi Bridge; the wide moat stocked with koi and lined with cherry trees are perfect for an afternoon stroll; the Higashi Goen (East Garden) marks the site of old Edo Castle and has wide paths for walking.
Tokyo Japan
Phone: 3213-1111 (Ext. 485, 486) Palace Tour Office
Online: Imperial Palace website
Admission: Free
Open: Tours Monday-Friday (10:00 a.m. and 1:30 p.m.- Tours take approximately 75 minutes and an application for a tour must be submitted at least one day before)