On my second day in Petra I went a little off the beaten path and instead of walking through the siq, I scrambled through the Wadi Muthlim slot canyon and emerged somewhat northwest of the Royal tombs where few tourists venture. Interestingly enough I came across an archaeological dig being conducted by students from BYU. It was in this area that I saw one of the huge cisterns that could store thousands of gallons of water. It looked as big as a two story house dug deep into the rock near one of the bigger houses.