Some have said Einstein's riddle is the worlds hardest riddle. It isn't. The story is that Albert Einstein created it as a young man, and claimed that 98% of the world population couldn't solve it. Though I'm not certain of the true origin, it is a tough one, and it is a good way to exercise your brainpower. Here it is:

- There are five houses next to each other on a street, painted five different colors.

- A person of different nationality lives in each house.

- The five home owners each drink a different beverage, smoke a different brand of cigar and keep a different pet.

Einstein's riddle is simply this: Who owns the fish?

Of course, you need the necessary clues:

1. The British man lives in a red house.
2. The Swedish man keeps dogs as pets.
3. The Danish man drinks tea.
4. The Green house is next to, and on the left of the White house.
5. The owner of the Green house drinks coffee.
6. The person who smokes Pall Mall rears birds.
7. The owner of the Yellow house smokes Dunhill.
8. The man living in the center house drinks milk.
9. The Norwegian lives in the first house.
10. The man who smokes Blends lives next to the one who keeps cats.
11. The man who keeps horses lives next to the man who smokes Dunhill.
12. The man who smokes Blue Master drinks beer.
13. The German smokes Prince.
14. The Norwegian lives next to the blue house.
15. The Blends smoker lives next to the one who drinks water.

First of all, a chart is the most useful tool for riddles like this. Make a chart with five columns for the five houses, and five rows for house color, nationality, type of drink, type of cigar, and finally, pets. This gives you 25 boxes to fill in. Since clue #8 states the man in the middle house drinks milk, you can start by filling in that one.

Now you are on your own. This is a decent riddle, and especially fun for those who like riddles with systematic solutions. Even if you can't get the solution, you'll get a good mental workout doing Einstein's riddle.