Awaji Island (淡路島, Awaji-shima) is an island in Hyōgo Prefecture, Japan, in the eastern part of the Seto Inland Sea between the islands of Honshū and Shikoku. The island has an area of 592.17 square kilometres (228.64 square miles). It is the largest island of the Seto Inland Sea.
As a transit between those two larger islands, Awaji originally means "the road to Awa", the historic province bordering the Shikoku side of the Naruto Strait, now part of Tokushima Prefecture.
The Ōnaruto Bridge (大鳴門橋, Ōnaruto-kyō; lit. "Great Naruto Bridge") is a suspension bridge that carries 4 lanes of the Kobe-Awaji-Naruto Expressway connecting Minamiawaji, Hyogo on Awaji Island with Naruto, Tokushima on Ōge Island, Japan. Completed in 1985, it has a main span of 876 metres (2,874 ft). 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. In 2004, 6.8 million cars and trucks crossed this bridge, translating into a daily average of about 18,600.
The bridge is complemented by the Konaruto Bridge ("Small Naruto Bridge") and Muya Bridge between Ōge Island and Shikoku.
Hyōgo Prefecture (兵庫県, Hyōgo-ken; Japanese pronunciation: [çoꜜː.ɡo, -ŋo, çoː.ɡoꜜ.keɴ, -ŋoꜜ.keɴ]) is a prefecture of Japan located in the Kansai region of Honshu. Hyōgo Prefecture has a population of 5,469,762 (as of 1 June 2019) and a geographic area of 8,400 square kilometres (3,200 square miles). Hyōgo Prefecture borders Kyoto Prefecture to the east, Osaka Prefecture to the southeast, and Okayama and Tottori prefectures to the west.
Kobe is the capital and largest city of Hyōgo Prefecture, and the seventh-largest city in Japan, with other major cities including Himeji, Nishinomiya, and Amagasaki. Hyōgo Prefecture's mainland stretches from the Sea of Japan to the Seto Inland Sea, where Awaji Island and a small archipelago of islands belonging to the prefecture are located. Hyōgo Prefecture is a major economic center, transportation hub, and tourist destination in western Japan, with 20% of the prefecture's land area designated as Natural Parks. Hyōgo Prefecture forms part of the Kobe metropolitan area and Osaka metropolitan area, the second-most-populated urban region in Japan after the Greater Tokyo area and one of the world's most productive regions by GDP.
Osaka Bay (大阪湾 Ōsaka-wan Japanese: [oːsakaꜜwaɴ]) is an inland bay in western Japan, on the eastern side of the Seto Inland Sea. It is separated from the Pacific Ocean by the Kii Channel and from the neighbor western part of the Inland Sea by the Akashi Strait. Its western shore is formed by Awaji Island, and its northern and eastern shores are part of the Kansai metropolitan area.
Major ports on Osaka Bay include Osaka, Kobe, Nishinomiya, Sakai, Amagasaki, and Hannan.
Tokushima Prefecture (徳島県, Tokushima-ken; Japanese pronunciation: [to.kɯ̥ꜜ.ɕi.ma, tokɯ̥.ɕiꜜ.ma, to.kɯ̥.ɕi.maꜜ.keɴ]) is a prefecture of Japan located on the island of Shikoku. Tokushima Prefecture has a population of 682,439 (1 February 2025) and has a geographic area of 4,146 km (1,601 sq mi). Tokushima Prefecture borders Kagawa Prefecture to the north, Ehime Prefecture to the west, and Kōchi Prefecture to the southwest.
Tokushima is the capital and largest city of Tokushima Prefecture, with other major cities including Anan, Naruto, and Yoshinogawa. Tokushima Prefecture is located on the Kii Channel, connecting the Pacific Ocean and Seto Inland Sea, across from Wakayama Prefecture on the Kii Peninsula of the island of Honshu. Tokushima Prefecture is connected to Awaji Island across the Naruto Strait by the Ōnaruto Bridge as part of the Kobe-Awaji-Naruto Expressway, connecting the prefecture to the city of Kobe and the San'yō Expressway on Honshu.
The Akashi Kaikyo Bridge (Japanese: 明石海峡大橋, Hepburn: Akashi Kaikyō Ōhashi) is a suspension bridge that links the city of Kobe on the Japanese island of Honshu and Iwaya, Awaji on Awaji Island. It is part of the Kobe-Awaji-Naruto Expressway, and crosses the busy and turbulent Akashi Strait (Akashi Kaikyō in Japanese). It was completed in 1998, and at the time, was the longest central span of any suspension bridge in the world, at 1,991 metres (6,532 ft). Currently, it is the second-longest, behind the 1915 Çanakkale Bridge in Turkey that was opened in March 2022.
The Akashi Kaikyo Bridge is one of the key links of the Honshū–Shikoku Bridge Project, which created three routes across the Seto Inland Sea.
The Akashi Strait (明石海峡, Akashi Kaikyō) is a strait between the Japanese islands of Honshu and Awaji. The strait connects Seto Inland Sea and Osaka Bay. The width of the Akashi Strait is approximately 4 kilometers, and maximum depth is about 110 meters. The fastest tidal current is about 4.5 metres per second (8.7 knots).
The 1.5-kilometer strait is one of the important points of the Seto Inland Sea and is at the mouth of the Pacific Ocean. The surrounding waters around Akashi Strait is a known fishery area. The Akashi Strait is designated as an international shipping channel by the Maritime Traffic Safety Act in Japan.
Naruto Strait (鳴門海峡, Naruto-kaikyō) is a strait between Awaji Island and Shikoku in Japan. It connects Harima Nada, the eastern part of the Inland Sea and the Kii Channel. A famous feature of the strait is the Naruto whirlpools. Ōnaruto Bridge, the southern part of the Kobe-Awaji-Naruto Expressway, crosses over it.
The Naruto whirlpools (鳴門の渦潮, Naruto no Uzushio) are tidal whirlpools in the Naruto Strait, a channel between Naruto in Tokushima and Awaji Island in Hyōgo, Japan. The strait between Naruto and Awaji island has a width of about 1.3 km (0.81 miles). The strait is one of the connections between the Pacific Ocean and the Inland Sea, a body of water separating Honshū and Shikoku, two of the main islands of Japan. The tide moves large amounts of water into and out of the Inland Sea twice a day. With a range of up to 1.7 m (5.6 ft), the tide creates a difference in the water level of up to 1.5 m (4 ft 11 in) between the Inland Sea and the Pacific. Due to the narrowness of the strait, the water rushes through the Naruto channel at a speed of about 13–15 km/h (8–9 mph) four times a day, twice flowing in and twice flowing out. During a spring tide, the speed of the water may reach 20 km/h (12 mph), creating vortices up to 20 m (66 ft) in diameter.
The current in the strait is the fastest in Japan and the fourth fastest in the world after the Saltstraumen outside Bodø in Norway, which reaches speeds of 37 km/h (23 mph), the Moskenstraumen off the Lofoten islands in Norway (the original maelstrom) reaching 27.8 km/h (17.3 mph); and the Old Sow whirlpool in New Brunswick, Canada with up to 27.6 km/h (17.1 mph).