Qingdao Jiaozhou Bay Tunnel
Qingdao Jiaozhou Bay Tunnel is an under-sea road tunnel located in Qingdao, Shandong Province in eastern China. It crosses underneath Jiaozhou Bay, connecting Huangdao District to the south with Shinan District in the north at the narrow entrance to the bay.
Source: Wikipedia — Qingdao Jiaozhou Bay Tunnel (CC BY-SA 4.0)