The four places are named in the Buddha's own last discourse, which is unusual: a tradition insisting that nothing is permanent nevertheless pointing at four patches of ground. Bodh Gaya, where the awakening happened, is the busiest — the Mahabodhi temple sits beside a descendant of the tree, and on any given winter day you will find Thai, Tibetan, Sri Lankan, Japanese, Burmese and Western pilgrims practising side by side in mutually unintelligible liturgies. All four sites were lost for centuries and re-identified in the nineteenth century by British archaeologists working from a Chinese pilgrim's seventh-century travel diary, which is one of the odder recoveries in religious history.