Volcanic crater lakes are bodies of water that form in the depressions left by volcanic eruptions. When a volcano erupts, it can create a large crater, known as a caldera, which may fill with rainwater or groundwater over time. These lakes can vary in size and depth, depending on the volcano's activity and the surrounding environment. These lakes often have unique ecosystems due to their isolation and specific chemical compositions. Some famous examples include Lake Toba in Indonesia and Crater Lake in the United States. The water in these lakes can be strikingly blue or green, influenced by minerals and volcanic activity.