The perl with a green glow

Emerald lake in Tongariro National Park (New Zealand) with its beautiful green glow. The lake is generated from past volcanic activity. Its special colour is created by sunlight reflection from a layer of carbonate deposited on the lake floor where diatoms are also contributing to. The lake is very cold and acidic, thus not suitable for swimming. The smoke around is thermal streaming causing the intense sulphuric smell around the lake.