Hegra, also known as Mada'in Salih, is a really old place that was built a long, long time ago in a far away land called Saudi Arabia. It's a special place because it has lots of really big rocks and some really cool buildings that someone a long time ago carved into the rocks with their hands.
Back when Hegra was built, people used to live there and trade things like spices and textiles with other people in nearby lands. The people who lived in Hegra were pretty smart and made sure to build their homes and buildings in a way that kept them cool during the hot desert days and warm during the cold desert nights.
Nowadays, people go to visit Hegra to learn about the people who used to live there a long time ago and to see the amazing buildings and carvings that are still there. It's like taking a cool field trip and learning about history in a fun way!