青函トンネル

The Seikan Tonneru is the longest tunnel in the world, at 33.5 miles (53.9 km). It is used by JR trains to connect Japan's two largest islands, Honshu and Hokkaido: its name is an abbreviation for 青森函館 "Aomori-Hakodate." While geologists had been researching potential railway tunnel routes between the two islands as far back as 1946, construction did not start until 1971, and the tunnel was not completed until 1986. It opened for commercial service in 1988.

The construction of the Seikan Tunnel employed some 1.4 million people in total, and required 1,276 km of cable and 168,000 tons of steel. It was impossible to bore the tunnel because of the unpredictable nature of the surrounding rock, so 6.3 million cubic meters of earth were blasted out, enough to fill the Tokyo Dome five times. At its deepest point, the tunnel runs 787 feet below the surface of the Tsugaru Strait.

In the end, the Seikan Tunnel cost over $7 billion to build. It actually consists of three tunnels: a two-track main tunnel, a smaller service tunnel next to it, and an even smaller pilot tunnel below the other two. Today, the service and pilot tunnels are used for maintenance and evacuations.

The tunnel boasts some interesting engineering features, too. Whereas most railways consist of short rails bolted together, the Seikan's rails are welded together, making them the longest rails on Earth. Both lines are designed to accommodate regular trains as well as wider Shinkansen trains (with the addition of a third rail, which hasn't been installed yet).

Shinkansen trains have yet to pass through the tunnel, but 30 limited express trains enter it each day. Decreasing airfares between Honshu and Hokkaido have made it an unpopular choice for most travelers: the fastest train combinations between Tokyo and Sapporo take ten hours to complete a 90-minute plane journey. However, JR's nightly sleeper expresses—the Hokutosei, Tsugaru, Nihonkai, Elm, Cassiopeia, and Hamanasu—have become a popular choice for tourists looking for a comfortable alternative to flying, and the extension of the Tohoku Shinkansen route to Hachinohe has made it easy to connect to limited expresses bound for Hakodate and the island beyond.

So don't write off the Seikan Tunnel yet.