How was Hezekiah’s Tunnel constructed without modern day equipment? How could two teams 131 feet underground, without GPS, meet in the middle connecting the two tunnels? How were the workers and subsequent users of the tunnel able to breathe oxygen? Why was the tunnel S-shaped and not straight? How were the workers able to maintain a precise 0.6% grade slope underground for 1,750 feet? These questions, ultimately, remain a mystery.