Why did they build a maze for the Minotaur with a possible escape route rather than just an ordinary prison? Why leave the possibility of escape open?
Well see, the Minotaur was arbitrarily strong. No material could build a wall strong enough that he couldn't bash through nor a door that he couldn't break down. But, he wouldn't try and break down anything if there was obviously a path right there he could use to go around it normally. By putting him in a maze, he will always keep trying the next path thinking it might be the exit, never attempting to break any wall. The puzzle is harder than any material they could have used to build a prison, as it cannot be bent by the Minotaurs brute force.
Computation (eg cryptography) can be "unbreakable" in a way that bank vaults and deposit boxes can't.