The Hpa-An caves are hollows inside limestone towers standing up from the flat rice paddies of Kayin State, in southern Myanmar, and people have been filling them with Buddhas since the seventh century. Rainwater dissolved the caverns out of the soft rock; worship did the rest. Kawgun is the oldest. Almost every surface of it — walls, ceiling, the cliff outside — carries small clay Buddhas and reliefs, pressed on by hand one at a time over centuries. The styles shift as you move along the wall, each era leaving its own signature on the same rock. Mon tradition says a queen sheltering here during a war had the first image made in thanks. A cement works blasting the neighbouring hills shook chunks of that work off the walls, and the gaps are still there.
Saddan runs clean through its mountain. You go in at one mouth, past a huge reclining Buddha and rows of gilded images under giant stalactites, and come out at the other. The floor is wet and uneven, and stretches of it are dark enough to need a torch. There is no road at the far end, so boatmen pole flat wooden boats across a reed-fringed lake and along channels between the paddies, round the mountain to where you started. The through-walk opens only in the dry months; the monsoon floods the rear galleries. Kaw Ka Thaung is the easy one, lined with gilded images, with spring water gathered into a walled pool outside that stays cold at midday and fills with local families. The caves lie kilometres apart, so you link them by motorbike on red-earth roads between the paddies, with the 722-metre peak of Mount Zwegabin to steer by. Kayin State sits under do-not-travel warnings, and access can change at short notice. The day ends on the riverbank at Linno Gu, the Bat Cave, where well over half a million bats of a dozen species leave together as the light goes, and the column takes the better part of an hour to cross the water.