Chiang Dao Cave is a temple you walk into: five caverns running under Doi Luang Chiang Dao, the highest limestone mountain in Thailand. The door is outside and the rooms are inside the rock. At the foot of the mountain a red-and-gold Lanna archway opens onto a covered walkway raised in the 1930s, with spired chedis and naga staircases lining the approach. All of it grew out of a hermitage over the last century. The first caverns are paved and lit, with aisles running between stalactite columns that meet floor to ceiling. Gilded Buddhas sit on seven-headed naga thrones where Lanna pilgrims have made merit for generations, and incense hangs in the cool air. The vault climbs past the lamps into darkness, and the light gives out in passages whose ends you cannot see.
Three of the five caverns have never been wired. They are the Horse, the Crystal and the Water caves, and a village guide takes you into them with a hissing gas lantern that is the whole of the light. The ceiling sinks until you stoop, the floor narrows to single file, and the flame moves shadows across wet stone while bats shift overhead. The guide stops to name shapes worn out of the limestone — a horse, a lion, an elephant — the resemblances the inner caverns are named for. In the monsoon the underground river rises and these three can flood shut. Older stories put a good deal more down here. They fill the deep chambers with a hermit's seven wonders: a stream running from a solid-gold Buddha, a storehouse of divine cloth, a hidden city of nagas. And they say a prince of Phayao followed a girl who had turned into a golden deer into this cave and never came out. He died in the dark and became the guardian spirit of the mountain, and people still leave offerings for him at the mouth.