Together with udon, soba, ramen is one of the three major noodles in Japan. It is based on Chinese noodle, but it was adapted to Japanese way. Although udon and soba are the local specialties in Japan, ramen is more widely recognized as the local specialty. The reason is that the udon and soba can be eaten almost same anywhere in Japan but ramen is not.
Major ramen flavors are miso, shoyu, tonkotsu and shio. Shoyu is soy sauce, tonkotsu is pork broth and shio is salt. Then, usually these flavors cannot be eaten at the same ramen diners. Ramen is offered at diners or restaurants but in case the diner is specialized in ramen, usually only one flavor is offered. Especially diners in certain cities, such as Kitakata, Sano and Wakayama offer Kitakata ramen, Sano ramen or Wakayama ramen which are well recognized as local specialties.
Other cities which have local ramen are Fukuoka, Sapporo, Asahikawa, Hakodate, Onomichi and Kurume. Also, Ogikubo district in Tokyo is famous place for its ramen. Tokyo style is soy sauce, shoyu flavor but Fukuoka and Sapporo are famous for tonkotsu or miso. Especially if you say miso ramen, definitely you must try it in Sapporo.