Engineering

Located more than 600 feet beneath sea level, this tunnel boasts the world's first undersea roundabout.

The bridge that cost Germany a World Heritage Site.

This incongruous small ferry across the Willamette River north of Salem, Oregon has been operating continuously since the 1850s.

An isolated "phantom bridge" doomed to crumble into ruin.

An out-of-the-way state park in Oregon that features both a picturesque waterfall and the ruins of a hydropower plant.

A giant glider—designed by the father of the Rubik's Cube's designer—now soars within a shopping mall.

The remains of a 19th-century carving of what was to be a signal light on the Firth of Forth Estuary.

This quarter-mile tunnel under the Bluff in Pittsburgh bends at a 45-degree angle.

Once the largest gravity dam in the world.

This unusual three-way wooden foot bridge spans two rivers at once.

At the largest railway museum in the United States, you can see everything from an early steam engine to a functioning Thomas the Tank Engine.

A railroad lift bridge that was only lifted once and became obsolete before construction was finished.

This remnant of an old railroad is the tallest surviving wooden trestle bridge in Victoria.

An enormous Soviet aircraft, the only one of its kind, stands at the deserted shore of the Caspian Sea.

A supersonic jet stands on a pedestal in this rural village as a monument to military aviation.

Part of a highway network meant to connect Miami to Montreal, this 10-mile stretch of road made from red bricks is still around 100 years later.