Nihonbashi is considered the center of Edo as the zero kilometer marker is located on the NihonbashiBridge. This was the starting point of the major roads that connected Edo, previous name of Tokyo, with the outer provinces.
「いつの世も 道の起点は 日本橋」(From centuries past, / The place where all roads meet- / Nihonbashi) 日本橋かるた
江戸時代、徳川家康は日本橋を、全国に通じる五街道の起点に定めました。現在でも、橋の中央に埋め込まれた「日本国道路元標」は日本中の道路のスタート地点なのです!
全国にある「東京まで〇〇km」という道路標識は、ここ日本橋までの距離を示しているのです!
This is the replica of the zero kilometer marker that you can see on the side of the Nihonbashi bridge, on the same side as Mitsukoshi. On both sides of the replica there are boards that indicate the distance between the Nihonbashi bridge to some of the main cities in Japan.
道路元標の実物は、橋の中央に埋め込まれています。危険ですので、見学の際は、北詰西側元標の広場にあるレプリカをご覧ください!
This is a picture of the replica. The original marker is located in the center of the NihonbashiBridge.
遊びながら歴史や地理が学べる日本橋かるた
http://www.nihonbashi-renaissance.com/karuta/ (Japanese website)
The “Nihonbashi Carta” is a deck of cards that represents Nihonbashi. The cards show important places in the area. Half of the cards have references and explanations about Nihonbashi and the other half have images. The goal is to match the cards and collect as many as possible.