Monarch Butterfly Biosphere Reserve

A UNESCO World Heritage Site in Michoacán and State of Mexico where 300 million monarch butterflies winter in oyamel fir forests at altitudes above 3,000 metres, creating one of the world's most spectacular wildlife phenomena as the trees turn entirely orange with the weight of resting butterflies. The migration — 4,000 kilometres from Canada and the northeastern United States — is the longest insect migration on Earth.