The Sundial Bridge is a cantilever spar cable-stayed bridge that spans the Sacramento River in Redding, California, about a 3 hour drive north of San Francisco. It is similar in design to Santiago Calatrava's Puente del Alamillo in Seville, Spain. However, the mast of this bridge is located off center, creating a uniquely unbalanced look. At 217 feet (66 metres), the mast of the bridge also serves as the world's largest sundial. The shadow moves at about a foot per minute, so one can actually see the rotation of the earth. The deck of the bridge is composed of translucent glass that is illuminated at night, casting an aquamarine blue light on the river below.