Regional varieties
What is the broth used in Udon made of?
Udon
There are wide variations in both thickness and shape for udon noodles.  Inaniwa udon (稲庭うどん): a thin type from Akita Prefecture.  Mimi udon (耳うどん, literally "ear udon"): a lucky preserved food in Kuzu, Tochigi. It looks similar to ears.  Himokawa (ひもかわ): an extreme flat and wide type from Kiryū, Gunma.  Hōtō (rarely 餺飥, commonly ほうとう): a flat and wide type, usually cooked with vegetables, particularly Japanese "kabocha" squash, from Yamanashi Prefecture.  Kishimen (棊子麺, or more commonly きし麺): a flat type from the Nagoya.  Ise udon (伊勢うどん): a soft type, usually eaten with sweet soy sauce, from Ise, Mie.  In Kansai region, a soft and medium thickness type is popular.  Sanuki udon (讃岐うどん): a thick and rather stiff type from Kagawa Prefecture.  Hakata udon (博多うどん): a thick and soft type from the Fukuoka.  Dango-jiru (団子汁): similar to the above "Hohtoh", from Ōita Prefecture. Nominally a "dumpling soup", it resembles very thick, flat udon.  Okinawa soba (沖縄そば): also called "suba", a regional Okinawan noodle made by adding some vegetal ash to the flour, similar to how ramen is made. However, it is very similar to udon.  There is also a dish called "udon" in Palau, because of the former Japanese administration. The broth is soy sauce–based like Japanese udon. However, as there were many immigrants from Okinawa, it uses less broth like Okinawa soba. Most notably, the noodle is that of spaghetti, as it is easier to acquire there.