Black+Eggs

In Owakudani, where an inactive volcano gives off plenty of steam, black eggs are sold. The black eggs are just regular eggs but with a black shell. The legend says that eating one will give you seven extra years of life.

How they make a black egg: You place regular chicken eggs into the gray groundwater of Hakone, where Owakudani is located, and let it boil until their shells turn black. Don't worry, because these eggs don't become toxic from the sulfur. Instead, they are thought to have regenerative properties. After awhile, the black shell will turn into a yellow color, but the inside is the same as a regular boiled egg, even when its shell is still black.