The traditional Danish smørrebrød consists of a piece of buttered rye bread, a dense, dark brown bread, on which topping (pålæg) is added.
Topping can be cold cuts, fish (pickled herring is a classic), cheese, spreads, boiled eggs, prawns, etc…
My favourite place to eat smørrebrød is Torvehallerne, a covered market with over 60 stands selling everything from fresh fish and meat to gourmet chocolate and exotic spices, as well as prepared food for a quick bite.
It seems watching dozens of (subtitled) Danish TV shows and movies isn’t enough to pronounce the word smørrebrød correctly. I for one have tried, and it took me ages to get a very patient Dane (they are so nice people!) to understand it.