The world's longest 3D-printed concrete bridge, which is now open to foot-traffic in a park in Shanghai, December 23, 2018. Measuring 14.1 meters long and 4 meters wide, the bridge crosses a canal in Wisdom Bay, which is a science and innovation park in Shanghai's Baoshan District. Modeled after the 1,400 year old Zhaozhou Bridge in Hebei Province, the span - created by numerous slabs of 3D-printed concrete - surpasses the length of two other 3D-printed concrete bridges in Spain and Holland. [Photo: VCG]

A mother leads her son across the world's longest 3D-printed concrete bridge, which is now open to foot-traffic in a park in Shanghai, December 23, 2018. Measuring 14.1 meters long and 4 meters wide, the bridge crosses a canal in Wisdom Bay, which is a science and innovation park in Shanghai's Baoshan District. Modeled after the 1,400 year old Zhaozhou Bridge in Hebei Province, the span - created by numerous slabs of 3D-printed concrete - surpasses the length of two other 3D-printed concrete bridges in Spain and Holland. [Photo: VCG]

Finishing touches being put on what is the world's longest 3D-printed concrete bridge, which is now open to foot-traffic in a park in Shanghai, December 23, 2018. Measuring 14.1 meters long and 4 meters wide, the bridge crosses a canal in Wisdom Bay, which is a science and innovation park in Shanghai's Baoshan District. Modeled after the 1,400 year old Zhaozhou Bridge in Hebei Province, the span - created by numerous slabs of 3D-printed concrete - surpasses the length of two other 3D-printed concrete bridges in Spain and Holland. [Photo: VCG]

Workers clean what is now the world's longest 3D-printed concrete bridge, which is now open to foot-traffic in a park in Shanghai, December 23, 2018. Measuring 14.1 meters long and 4 meters wide, the bridge crosses a canal in Wisdom Bay, which is a science and innovation park in Shanghai's Baoshan District. Modeled after the 1,400 year old Zhaozhou Bridge in Hebei Province, the span - created by numerous slabs of 3D-printed concrete - surpasses the length of two other 3D-printed concrete bridges in Spain and Holland. [Photo: VCG]