The water tunnel that Macky and others used to move through Jerusalem without the Romans knowing was created by a king called Hezekiah over 2,500 years ago. Hezekiah was very worried that Jerusalem was going to be attacked by the Assyrians and he wanted to be sure that his own people had fresh water which the Assyrians couldn't get at. So Hezekiah ordered that a tunnel 533m long be dug through solid rock. What an amazing thing to do, especially since we know from archaeology that they began digging at opposite ends and managed to meet in the middle!
The water came from the spring of Gihon, which was then covered over so it couldn't be seen - it ended up in the pool of Siloam, inside the city walls, very near the Temple. You can read about the pool of Siloam in John 9:7 when Jesus heals a blind man. Jesus puts mud on the man's eyes and tells him to wash in the pool.
The tunnel still exists today and you can find photos on the internet of people walking through it.
Click the picture to see a larger version - you might want to save it or print it too!