Published caption : Formed by a volcanic eruption some 1,200 years ago, Umi Jigoku is a natural hot spring in Oita prefecture which boasts water of a startlingly bright cobalt-blue. It is one of the stops on the Jigoku Meguri (‘‘Hell Tour’’), an organised outing, popular with groups of friends or family members, that takes in eight hot springs in the area, all located within easy walking distance of each other. Other highlights on the itinerary include visits to a hot-mud pond, a hot spring where the water is blood-coloured and a pond with crystal-clear water. Tickets for the Hell Tour cost ฅ2,000 (around 640 baht) each for adults. Umi Jigoku is the starting point of the tour and to get here by bus from Beppu’s JR train station takes around 20 minutes.