From Denny: This is pretty cool to see after centuries hidden away, constructed of very large stones. It's believed to have been a working part of the Roman Empire as far back as about second century A.D., used to bring fresh water into the city of Jerusalem.
The 1800 year old water channel was discovered in the Old City near the Jaffa Gate. What's amazing is that it still stands after all this time. The Romans were great engineers.