You are stood between two gates. There is a guard stood in front of each gate.
One gate leads to Heaven, the other gate leads to Hell. The person guarding the gate to Heaven always tells the truth. The person guarding the gate to Hell always tells a lie. However, you don't know which gate is which, therefore you don't know which guard is going to tell the truth/fib.
Presume that you want to go through the gate to Heaven.
You have one question to ask either guard. What question do you ask?
(Don't shout out the answer if you know, please!)