Hegra was the second city of the Nabateans, who built their renowned capital, Petra, more than 500km to the north-west in what's now Jordan. Located in Saudi Arabia's AlUla region, the ancient stone city (known to Muslims as Al-Hijr and also as Mada'in Salih) has roots going back as far as the 1st Century BCE. It's also the country's first Unesco World Heritage Site, home to more than 100 well-preserved tombs with elaborate facades carved into the sandstone outcrops.