I came across an interesting riddle I'd like to share with you.
I'm going to post the solution next week on this thread. Maybe you want to give it a try?

You are walking through a desert and are in desperate need of water. You arrive at a fork in the road. One road leads to certain death (by whatever means), the other road will take you to a well. Of course, your life is too precious to simply choose one of the roads, since chances are 50:50 that you survive.

In the middle of the fork there is a house. Two brothers, absolutely identical twins, live there. You've already heard about them an know that one of them will always tell the truth whereas his brother will always lie. There is no way to distinguish the twins, neither by appearance nor way of speaking nor by anything else. You don't know who of them is going to open the door.

You are only allowed to knock one time.
You are only allowed one single question.

What is the question that will save you from certain death?