One of the world's biggest bangs took place in 1886 when the top of Mt Tarawera blew off in a huge volcanic explosion, burying several villages in the process and leaving behind this truncated cone with a chasm four miles long and 800 feet deep. The authorities closed public access after a few motocross riders misjudged the track and sailed off into the crater but you can geto the top by helicopter (as Billy Connolly did).