The classical natural wonders are usualy huge and hard to miss – vast canyons, giant mountains or so. Many of the most fantastic natural phenomena, however, are also least easy to spot. From moving rocks to mammatus clouds and red tides to fire rainbows, here are seven of the most spectacular phenomenal wonders of the natural world.

A very rare phenomenon known as a ‘blue sun.’ These have been observed from time to time around the world. The most recent widely accepted documentation of a blue sun occurred in September 1950 in Edinburgh, Scotland.