Hibiya park in Tokyo covers an area of 161,636.66m2 between the east gardens of the Imperial Palace to the north, and the Shimbashi district to the south-east. Its easy to get there by foot from Yurakucho station. This park has three ponds and quite a few trees. Autumn is especially lovely in this park, and should not be missed if you happen to be in Tokyo this time of the year.
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Find out more about Hibiya Park.