While traveling, you have reached a bifurcation on the road. One path leads to glory, gold and the princess, whereas the other one will lead to somewhere bad. Very bad.

On the wayside you notice two people. One will speak nothing but lies, the other one will always tell the truth. You have just one question that you can ask to either one or the other, not both of them. How can you then figure out which path is the one you want to take?