A dangerous riddle

There was once a storyteller who inadvertently offended a rich and powerful king. The king was furious and in his rage, condemned the storyteller to death!
On the day of his execution, as was the custom of the time, the storyteller was granted one final request. He said, “I ask only that I be allowed to live as long as it takes the king to solve a riddle”. Now the king rather fancied himself at solving riddles and so he readily agreed.
But through all of his lifetime, he was unable to solve the storyteller’s riddle. It became his lifelong obsession until he eventually lost his mind, lost his queen and lost his kingdom. He died in misery in a place set aside for the incurably insane! As for the storyteller, he lived to a ripe old age, dying peacefully in his sleep.
The riddle became such a threat to the sanity of man that a law was passed forbidding it ever to be repeated. And it never was. Until a few years ago when an archaeologist discovered an old manuscript upon which was written the story that I have just told you. It also contained the storyteller’s riddle.
I could tell you what it said and you might try to solve it yourself. But before you do, just remember what happened to that rich and powerful king, all those hundreds of years ago. Are you sure that you want to risk losing your sanity?!

All right, here it is: I can touch you but you can't touch me. Although I have no wheels, wings or sails, I can take you on a long journey. And sometimes you can see me best with your eyes closed! What am I?