The Onaruto Bridge is a suspension bridge on the route connecting Kobe with Naruto, Tokushima, Japan.
Carries 4 lanes of roadway
Crosses Naruto Strait
Locale Naruto, Tokushima and Awaji Island
Design Suspension bridge
Longest span 876 metres (2,874 ft)
Clearance below 41 metres (135 ft)
Opening date 1985
Although it is one of the largest bridges in the world, it is dwarfed by the Akashi-Kaikyo Bridge, which is on the same route.
Recurring whirlpools known as the Naruto whirlpools are located below the bridge, caused by tidal currents between the Seto Inland Sea and the Pacific Ocean passing over undersea ridges under the Span, causing very strong eddy currents, some of which make large deep whirlpools.
According to the change of tides, the whirlpools occur roughly every six hours and can typically be seen once in the morning and once in the afternoon for an hour or two. The whirlpools vary in size, depending on the intensity of the tides. They tend to be larger in summer than in winter, and are largest during spring tides, which occur every two weeks.
If all factors play together favorably, whirlpools of up to 20 meters in diameters can be observed.
The whirlpools are not dangerous to boats, and are best viewed from sightseeing boats which get right up next to and among the whirlpools. There are two companies that run tours to the whirlpools from nearby piers on Shikoku and one from Awaji Island on the opposite side of the straight.