In the town of Reykjavik, Siggi, a traditional Icelandic cook, is preparing one of the signature meals of the Thorrablot festival as the Vikings once did.

SOUNDBITE (English): Siggi Hall, Chef - "Feel the pungent aroma of the shark."

This freshly caught 1700-pound Greenland shark is naturally full of urea and other toxins.

These chemicals act as antifreeze, allowing the shark to live in waters as cold as minus two degrees Celsius.

The toxins are so concentrated that to eat this meat could make you seriously ill-or possibly even kill you.

But Hildibrandur Bjamus's family has a secret shark recipe that goes back generations.

And he knows that the only way to prepare it… is to let it rot.

As the meat decomposes, it oozes toxic ammonia…the chemical found in most household cleaning products and human waste.

SOUNDBITE (English):Siggi Hall, Chef - "I don't want to say the word which will probably describe it best…pee."

In Viking times, shark meat was buried out of sight.

But Hildibrandur prefers to see his delicacy.

That way he can keep track of the decaying process.

SOUNDBITE (English):Siggi Hall, Chef - "His nose decides when it is ready to try it-it's like wine-making, you know?”

When the meat is at a perfect rotten state, it's hung to complete the breakdown process.

After six months, it's ready to be served.

SOUNDBITE (English):Siggi Hall, Chef - "This is going to be very good. In just two more months, it's going to be a great, great shark, this one."

SOUNDBITE (English): Vox Pop, Restaurant Patron - "It's a social thing for us to come together and eat this."

SOUNDBITE (English): Vox Pop, Restaurant Patron - "I don't like the shark."

SOUNDBITE (English): Vox Pop, Restaurant Patron - "It's like ammonia."

SOUNDBITE (English): Vox Pop, Restaurant Patron - "Tastes and smells like piss…it does."

Despite this feast of oddities, these Icelandic partygoers see nothing bizarre about tonight's main courses.

No matter what dish is served, Siggi and the Icelanders agree - there is more to this tradition than just taste.

SOUNDBITE (English)

"The point is taking care of this tradition, having fun with it, know what it is, don't forget it, don't forget where it comes from."