Imperial Palace Garden East- Really ONLY a garden
I can't exactly say its a "trap" per se cos it cost you nothing to enter the gardens. However, if you think you can see any buildings, structures remotely japanese or imperial, then drop this off your itinerary. There is NOTHING worthy to see in the gardens. Its just a huge park. Even the landscaping is non-Jap. A better option is to register a guided tour with the IHA (website) and get a guided tour of some parts of the inner palace. Although it is conducted only in Jap, I think it will be a more insightful trip.