Crafted from part of the original castle compound, these lovely free gardens allow you to get close-up views of the massive stones used to build the castle walls, and even climb the ruins of one of the donjons (main keeps), off the upper lawn. The number of visitors at any one time is limited, so it never feels crowded. Most people enter through Ōte-mon, the closest gate to Tokyo Station, and once the principal entrance to Edo-jō.
Don't miss the Ninomaru Grove, a woodland area that is one of the prettiest parts of the garden, with a pond and the elegant teahouse, Suwa-no-chaya. The large lawn is where the Honmaru, the castle's central compound, was once located.
Just inside the gate you may want to drop by the Museum of Imperial Collections, which mounts small exhibits of the 9500-plus artworks owned by the imperial family.
Free two-hour guided walking tours of the gardens are offered on Wednesday, Saturday and Sunday; meet at the JNTO Tourist Information Center before 1pm. The gardens are closed on Mondays and Fridays except for national holidays; see website for further detail.