There is a theory called 'Sendai capital theory' that Sendai would be the capital of Japan now if only the Ouetsu-reppan alliance had won a battle against the new government.
「戊辰戦争で奥羽越列藩同盟が新政府に勝っていれば仙台（周辺）が日本の首都になった」、という「仙台首都説」がある。