Great Seto Bridge

Stand on the hill above Kojima and listen. Far below, a soft rumble rolls across the water, then fades. A train is crossing the sea on a deck of steel, beneath a highway full of trucks. The air smells of salt and pine. Ahead, a chain of towers and cables steps from island to island, until it disappears into the haze over Shikoku.

This is the Great Seto Bridge, known in Japanese as Seto Ohashi. Strictly speaking, it is not one bridge at all. It is a family of bridges, joined by viaducts, that links the southern edge of Kurashiki on the island of Honshu with the city of Sakaide on Shikoku. In total, the crossing runs for more than thirteen kilometres over the Seto Inland Sea.

Here is the first surprise. The structure has two levels. The upper deck carries the Seto-Chuo Expressway, with cars and lorries moving in both directions. The lower deck carries railway tracks. Trains between Okayama and Shikoku run through the inside of the bridge, framed by steel trusses. Many visitors who cross by train never see the bridge at all. They only see it from within, as a long rhythm of girders flashing past the window.

Before the bridge opened in 1988, the only way across was by boat. Ferries carried people, cars, and freight between the two coasts. The waters here are busy and often foggy, and the crossing could be dangerous. For most of the twentieth century, Shikoku was the only one of Japan's four main islands with no fixed link to Honshu. The bridge changed that in a single day.

The story behind the bridge carries a hard memory. In 1955, a ferry called the Shiun Maru collided with another vessel in fog near Takamatsu and sank. Many passengers died, among them a large number of schoolchildren on a school trip. The disaster shocked the country. It added strong public pressure to the long-discussed idea of a bridge. For many people in this region, the bridge stands as a quiet answer to that day.

Construction began in the late 1970s and took about ten years. Engineers had to work in deep water, strong tidal currents, and one of the busiest shipping lanes in Japan. Foundations were sunk into the seabed between the islands. Towers were raised, cables were spun, and steel sections were lifted into place. The work took place while ships kept moving underneath. When you look at the spans from here, picture tugboats and barges working in the same channels below.

Now look at the shapes of the different spans. They are not all the same. Some are suspension bridges, with a deck hanging from two great cables draped between tall towers. Others are cable-stayed bridges, where straight cables run directly from the towers to the deck in a fan pattern. There are also long truss bridges, built from triangles of steel. Engineers chose each type for the depth of the water and the width of the channel at that point.

The bridges step across a group of small islands that sit in the middle of the strait. These islands once lived almost entirely by fishing and the sea. Today the highway touches some of them, and a few have their own small communities below the deck. On one of them, Yoshima, there is a parking area on the expressway. Drivers can stop there and walk out to see the bridge from close range, with the islands all around.

The hill where many people come to see this view is Washuzan, on the Kojima side of Kurashiki. From its summit, the whole sweep of the crossing opens out. On a clear day you can follow the bridge from the coast below you to the far shore. You also see dozens of green islands scattered across the water. This view of the Inland Sea is one of the reasons the area became part of Japan's first national park, Setonaikai.

A second surprise sits right at the foot of the bridge. The town of Kojima, now part of Kurashiki, is known across Japan for denim. Local workshops have woven and dyed cotton here for generations, and today small makers produce jeans that are sold all over the world. Before or after visiting the bridge, you can walk along streets of denim shops, some with blue jeans hanging outside like flags. Even some of the local snacks and souvenirs are coloured indigo.

The bridge also feels very different at different hours. In the morning, mist can rise from the sea, and the towers appear one by one as the light grows. At midday, the water turns a bright blue-grey, and ferries and cargo ships draw white lines on its surface. In the evening, the sun sets over the western islands, and the steel turns gold and then dark. On some special nights, the bridge is lit up, and its outline glows over the black water.

It is worth thinking about the scale for a moment. Every day, thousands of people cross this sea without thinking twice. Commuters, freight drivers, families going home for holidays, tourists heading to the temples and gardens of Shikoku. A journey that once depended on the weather and the ferry timetable now takes minutes. The bridge did not only connect two coastlines. It drew Shikoku closer to the rest of Japan, and it changed how people in this region live and work.

Before you leave, take one more look. Follow the line of the deck from the shore near your feet out across the first island, then the next, and the next. Listen for the low sound of a train inside the steel. Watch a small fishing boat pass under a span that looks impossibly high above it. When you walk away, the bridge will stay on the horizon behind you, a thin line holding two islands together across the sea.