If you read typical description of Petra today (for example in the National Geographic: https://www.nationalgeographic.com/travel/world-heritage/petra-jordan/ ) it will tell you that this marvelous ancient city gradually declined and was abandoned soon after the Islamic conquest, around 600-700 AD., only to be ‘rediscovered’ in 1812, that is more than a thousand years later, by a Swiss explorer Johann Burckhardt. One can imagine, how surprised and astounded Johann must have been, when Beduins guided him through desert canyons and when he finally saw the great façade of the ‘treasury’ building carved in the desert