WELL, THIS IS THE 21ST CENTURY, YOU KNOW: Gravity-defying 3D printer to print bridge over water in Amsterdam. “A 3D-printing company based in Amsterdam has developed a revolutionary, multi-axis robotic 3D printer that can “draw” structures in the air — and it’s planning to build a bridge over a canal in the heart of the city. . . . This is the technique that will be used to print the bridge out of steel. Small increments of molten metal are welded to the existing structure, creating lines of steel. By printing multiple lines, the printer will be able to create a strong, complex structure that spans the canal — printing its own supports along the way so that it can operate autonomously.”