MAKKAH: They are among the region’s most striking natural wonders, formed over millions of years by ancient rivers — and still home to mysterious secrets. Now Saudi Arabia’s caves, sinkholes and caverns are becoming hidden gems for the adventurous or merely curious to seek out and explore. More than 230 caves — deep and shallow, and formed of limestone, gypsum and other minerals — have been discovered in the Kingdom’s deserts. As the mysteries of Saudi Arabia gain wider recognition, these natural treasures are the subject of growing interest. Mahmoud Ahmed Al-Shanti, a specialist in caves and dunes at the Saudi Geological Survey (SGS), told Arab News that caves are a valuable natural asset, and attract explorers, researchers and others interested in the field.