The oasis of Najran, surrounded by mountains and close to the Yemeni border, is one of Saudi Arabia's hidden gems. With towering mud-brick, fortress-like homes strung out along the wadi (riverbed, dry except during the rainy season) and an exceptional mud-brick fort, Najran is also home to a fascinating cultural mix that owes as much to the northern Yemeni highlands as it does to the rest of Saudi Arabia.