Carved directly into the sandstone of the hilltop, Thola's ancient cisterns date to the Himyarite period — the pre-Islamic south Arabian civilisation that flourished from roughly the second century BCE through the sixth century CE. The cisterns are lined with a hard lime plaster that has held up remarkably well: the coating is still visibly intact in large sections, smooth to the touch and impermeable. They were designed to collect rainwater running off the rock surfaces above and to hold it through the dry season, a function that made the hilltop community self-sufficient in the one resource that matters most in a siege.
The cisterns connect to cave systems in the rock, some of which also served as grain stores and refuge spaces. The whole complex — cisterns, caves, grain reservoirs — is a piece of integrated infrastructure that kept the community on the hilltop viable through conditions that would have forced a less prepared settlement to surrender or relocate. The Himyarites were among the great hydraulic engineers of the ancient world (the Great Marib Dam was their most celebrated work), and Thola is a smaller but equally purposeful expression of that tradition. You can walk among the cistern openings and trace the channels that once directed the runoff — the engineering logic is still readable in the rock.