大成建設
On 27 September 1925, construction finally began on a 2.2-km tunnel running between and , which was referred to by the name Kaminarimon, the iconic gate of Sensoji Temple. Okura Doboku, the forerunner of the present-day Taisei Corporation, was tasked with the job. Its elderly founder Kihachiro Okura insisted that it be built by Japanese workers, but at least one German engineer was recruited. Construction cost ¥4 million per mile (approximately ¥2.4 billion as of 2017). After several delays, the underground line finally opened on 30 December 1927 as the first subway in East Asia.