The 8 queens problem.
The problem consists in place 8 queen in a chessboard, but neither queen is able to attack other queen.
I found this solution after 30 min, but don´t see it untill you solve the problem by yourself, totally are 12 unique solutions (92 counting rotations and relfections).
There is an algorithm to construct the solutions, many variants, the general case (to place n queens in a nxn board) if you are interested you can check the wikipedia http://en.wikipedia.org/wiki/Eight_queens_puzzle to learn more.
P.D. Ignore the kings, but in chess.com diagrams they always appear.