Omoide-Yokocho is a hidden alley filled with street food stalls which sprawl across a relatively small area. It's worth a visit though if you wish to experience how locals take their meals. The food sold here are local street food delicacies and are worth a try.
Wikipedia https://ja.wikipedia.org/wiki/新宿西口商店街
Info http://www.japan-tourist-guide.com/omoide_yokocho.php
More information http://www.shinjuku-omoide.com/english/
Address Nishishinjuku, 1 Chome−1 新宿区新宿3丁目 〒151-8580 Tokyo, Shinjuku-ku, Japan
Coordinates 35°41'35.604" N 139°41'58.148" E