siege of Petra
... that at the end of the siege of Petra in 551 AD, the Romans discovered that there was yet another pipe beneath the ones they destroyed that was supplying water to the besieged garrison all along?
... that at the end of the <b id="mwA04"><a href="./Siege_of_Petra_(550–551)" id="mwA08" rel="mw:WikiLink" title="Siege of Petra (550–551)">siege of Petra</a></b> in 551<span id="mwA1A" typeof="mw:Entity"> </span>AD, the Romans discovered that there was yet another pipe beneath the ones they destroyed that was supplying water to the besieged garrison all along?