An hour outside Tokyo, and we were in Hell, which is a thrilling place to be if you&rsquore only visiting. Owakudani (its less startling name) steams and bubbles with sulphurous hot water so intense that nothing can live there. But it boils eggs really well the sulphur-blackened eggs are an earnest tradition among the onsen (hot spring)-loving Japanese. &ldquoEat one egg, add seven years to your life. Eat two, get 14. But eat three, and you live till you die,&rdquo said our guide. A colleague ate five but has lived to report the fact that the devil&rsquos food tastes &ldquojust like normal boiled eggs&rdquo. Y500 for six eggs.