Often known as Mother of Pearl clouds, nacreous clouds are an extremely rare sight. They form between nine and sixteen miles high in the atmosphere and give off a breathtaking iridescent glow. While they form mostly in the polar regions, they have been known to form across the globe during winter and at high altitudes. These beautiful clouds tend to shine brightly just before dawn or in the two hours just after sunset, making for an unforgettable sight.
London building tops / Tim Gallagher who took the picture says "I took these shots on the of December.This fog delayed my next flight but at least I got these shots. This is Canary Wharf, the new financial center in London"
The Big Picture photography competition: round 210