this strange-looking beast in tokyo is an artificial island and tourist attraction by the name of umihotaru (translation: marine firefly) which forms part of the tokyo bay aqualine, a bridge-tunnel that connects kawasaki and kisarazu.
cars can either drive over the 4.4km bridge to the island and park in order to admire the view or drive straight through to the tunnel entrance where they will be taken under the water for 9.5km until they reach kawasaki.
the tunnel is apparently the longest underwater tunnel in the world.
Source:- Deputy Dog