The biggest lake crater in Indonesia with its magical blue fire should definitely be on top of your list. At 2,300 metres above the sea level, this one-of-a-kind landscape was formed some 300,000 years ago by volcanic activities that left the area highly acidic. The unique combination of yellowish rocky surfaces and mineral lake is best enjoyed around 7 to 9 AM, while the blue fire caldera can only be witnessed in the wee hours of the morning.