This is one of my favorite stops. I've been here in the winter, spring, and late summer. Each time you'll find a different flower in bloom from the plums to the cherry blossoms and more.
Historically, the garden was used by the Shogun for falconry. Nowadays it's a perfect dichotomy of the old and new. Amidst the skyscrapers of the shinbashi area you'll find this quaint garden. The ponds around the garden are fed by the ocean via locks. You can see the modern pumps that do it now. This means that the rocks have barnacles giving it a unique serenity that you don't see in most of the gardens and parks in Japan.
As previously mentioned in the directions above this is the perfect stop after your breakfast in Tsukiji if you're taking on the Tokyo Death March. It also leads into the Sumida River Tour, which has a stop at the eastern edge of the garden.
There's not much to say more about this, but to experience it for yourselves. It's a place to discover your calm as you listen to the sounds of the sea and the city around you.
Hamarikyu Garden is located next to the Tsukiji area in Tokyo. This makes it the perfect stop after your morning breakfast of sashimi near the Tsukiji Fish Market. If you walk west of tsukiji on the main road you'll eventually come to a stone bridge with a view of the freeway overhead. Conversely, you can walk from shinbashi station, which is quite a walk, but it's a little harder to find.