<P> The Sundial Bridge provides pedestrian access to the north and south areas of Turtle Bay Exploration Park, a complex containing environmental, art and history museums and the McConnell Arboretum and Gardens . It also forms the gateway to the Sacramento River Trail, a 35 - mile - long (56 km) trail completed in 2010 that extends along both sides of the river and connects the bridge to the Shasta Dam . Drift boats of fishermen are often seen passing beneath the bridge as they fish for salmon, steelhead and rainbow trout . In the distance, Mount Shasta is barely visible . Shasta Bally is visible to the West looking upstream the Sacramento . </P> <P> The support tower of the bridge forms a single 217 - foot (66 m) mast that points due north at a cantilevered angle, allowing it to serve as the gnomon of a sundial; it has been billed as the world's largest sundial, although Taipei 101 and the associated sundial design of its adjoining park are much larger . The Sundial Bridge gnomon's shadow is cast upon a large dial to the north of the bridge, although the shadow cast by the tower is exactly accurate on only one day in a year--the summer solstice, June 20 or 21 . The time is given as Pacific Daylight Time . The tip of the shadow moves at approximately one foot per minute so that the Earth's rotation about its axis can be seen with the naked eye . </P> <P> The Sundial Bridge is a cantilever spar cable - stayed bridge, similar to Calatrava's earlier design of the Puente del Alamillo in Seville, Spain (1992). This type of bridge does not balance the forces by using a symmetrical arrangement of cable forces on each side of its support tower; instead, it uses a cantilever tower, set at a 42 - degree angle and loaded by cable stays on only one side . This design requires that the spar resist bending and torsional forces and that its foundation resists overturning . While this leads to a less structurally efficient structure, the architectural statement is dramatic . The bridge is 700 feet (210 m) in length and crosses the river without touching the water, a design criterion that helps protect the salmon spawning grounds beneath the bridge . The cable stays are not centered on the walkway but instead divide the bridge into a major and minor path . </P> <P> The cable for the bridge totals 4,342 feet (1,323 m) and was made in England . The dial of the sundial and a small plaza beneath the support tower are decorated with broken white tile from Spain . The bridge's deck is surfaced with translucent structural glass from Quebec, which is illuminated from beneath and glows aquamarine at night . The steel support structure of the bridge was made in Vancouver, Washington and transported in 40 - foot (12 m) sections by truck to Redding . </P>

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