Sipapu Bridge in Natural Bridges National Monument, Utah, USA

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Bridges to the past

The story of this striking sandstone formation in the US state of Utah begins around 10 million years ago. That's when tectonic shifts began slowly lifting the 130,000 square-mile Colorado Plateau above the surrounding plains. Later streams from the Colorado River cut through the elevated land, creating deep canyons. When water broke through a canyon wall, sometimes a natural bridge like this one remained above the gap between canyons.

The Natural Bridges National Monument – a protected area similar to a national park - protects three major bridges: Sipapu (pictured, and the largest), Kachina, and Owachomo. But its status can't stop the slow ravages of time. Thousands of tonnes fell from the inside of Kachina in 1992, slimming the bridge, and the remains of many other fallen bridges are scattered across the area, hinting at the fate awaiting those which remain. When the sun goes down, the stars shine extra bright here, with some of the lowest levels of light pollution ever recorded.