Night-shining Clouds above Gotland Heritage

A summer evening on the island of Gotland, the Baltic Sea, is painted in electric blue by the mysterious night-shining clouds known as the Noctilucent clouds or NLCs. They lie near the edge of space, reflecting sunlight from about 80 kilometers above Earth’s surface. They are usually spotted above the Polar Regions in summer. In the foreground is the World Heritage Site of Visby known for the 3.4 km long town wall that encircles the town center, built between 12th to 15th century. Click on the second photo to see another view of Visby walls and NLCs.