A Landscape Carved from an Ancient Sea
The dramatic towers of the Hpa-An karst landscape are the remnants of a shallow tropical sea floor. The rock itself belongs to the Moulmein Limestone formation, which dates to the Permian period, roughly 250-300 million years ago. This geological foundation was formed from immense deposits of coral and marine organism skeletons that hardened over eons. Tectonic activity lifted this seabed, and for millions of years, the warm, wet climate has facilitated a slow but persistent process of chemical weathering. Rainwater, made slightly acidic by atmospheric carbon dioxide, has dissolved the calcium carbonate in the limestone, carving the rock into the sheer-sided towers, or karsts, seen today.
This process of dissolution also formed a vast network of caves within the limestone massifs. Some of the largest, like Saddan Cave, create passages that run completely through the mountains for up to 800 meters. The tallest of these karst towers, Mount Zwegabin, rises 722 meters from the surrounding plains. The caves feature extensive speleothems—secondary mineral deposits like stalactites and stalagmites—formed as mineral-rich water drips and loses its carbon dioxide to the cave air. At least 17 distinct types of speleothems have been classified within the caves of Hpa-An.
Sanctuaries in Stone
The caves of Hpa-An are geological formations, they are also ancient cultural and religious sites. Kawgun Cave is notable for its extensive collection of ancient art. Its walls and ceiling are covered with thousands of clay votive tablets depicting the Buddha, some of which have been dated to the 7th century. Inscriptions in the ancient Mon script are also present, providing historical records of royal patronage and religious devotion. While many of the images are Buddhist, at least one stone relief incorporates Hindu deities like Brahma, Vishnu, and Shiva.
Other caves, like Yathaypyan and Saddan, are also filled with hundreds of Buddha statues and pagodas. These are not static museum pieces but represent centuries of continuous worship, with new statues being added by pilgrims over time. The environment of these caves has also created a unique biological niche. They host vast populations of bats and are habitats for specialized invertebrates. Among these are large huntsman spiders of the genus Heteropoda. While research is ongoing, some specimens collected from Myanmar's caves are comparable in size to Heteropoda maxima, the species from Laos currently considered to have the largest leg span of any spider.