Swedish Surströmming (soured herring)

How do you know when your surströmming (soured herring) is ready to be devoured? When the cans bulge around the middle, an effect caused by a gassy, bacterial byproduct of its lengthy fermenting process.

To prepare this traditional Swedish meal, herring from the Baltic Sea are gutted and tinned in brine, then stored somewhere (preferably warm) for several months. Its pungent aroma makes dining alfresco an absolute must. Locals recommend opening the can under water whenever possible to contain the tantalizing odor of rotten egg, rancid butter and vinegar that results from the fermentation process.

Don't worry about running into it stateside: Often classified as rotting, not fermenting, and considered a potential weapon (because of the pressurized contents), surströmming is banned by a number of airlines and customs agencies.