It's a true wonder of nature when millions of monarchs leave their home grounds in the USA and Canada and gather in the middle of Mexico to enjoy the warm local winter. As they densely cover the grounds, one might think there is a kind of orange carpet. The fir trees around also turn orange invaded by the beautiful creatures from top to bottom.
Such an incredible congregation of monarch butterflies in Mexico's oyamel forests led to a creation of the Monarch Butterfly Biosphere Reserve in the area, and in 2008 it was also recognised as a World Heritage site of UNESCO. The largest populations can be observed between November and February.