Ever since I moved to Sweden I have heard about eating surströmming. Sweden is historically known for their fishing industry and not the least of which is their herring. 
Naturally, back in the day, they had to learn to preserve their food. So when herring is fermented, covered in salt, and canned up for periods of time, it turns into surströmming. Which isn’t the most horrible thing to eat, but the smell is something that only gets more potent by the minute and is an incredibly horrid thing to breath up your nostrils. 
In fact in 2002, a Japanese study concluded that it was the worst smell among food. But people still insist on smelling it, despite the fact that the surströmming is placed far away from the table you’re eating at (look how many flies flock to this food: that can’t be a good thing). No wonder Swedes drink Schnapps and sing songs while eating this food. 
Surströmming starts being sold around the third Thursday of August and thereafter people host Surströmmingsskiva.
People from the northern parts of Sweden may eat it year round, while many urban Swedes have never tried it.
Some people love it, but when I tried it with my co-workers, there were five who had never eaten it and only three ate a whole sandwich. 
You can eat surströmming by itself, but it’s usually served on flatbread with various toppings like potatoes, butter, sour cream/crème fraîche, and diced onions (and maybe tomatoes or dill).
To get a sense of the smell, you can view this youtube video (warning and spoiler alert, one of the guys does throw up):
http://www.youtube.com/watch?v=3vEl6Ey8Gdc Click here to see a more fun August holiday known as Kräftskiva.
Swedish Traveling, Culture & More Adventures 