At 120.5 metres (395 ft) the Phra Pathommachedi is the tallest stupa in the world. Little is known of the its construction many legends have arisen, the most famous is which is the Legend of Phaya Gong and Phaya Phan (apologies for the somewhat tortured English):

The story is about a king of Nakhon Chai Si, Phaya Gong, had a baby boy, Phan, but the court astrologer predicted that Phan will commit fratricide in the future. Phaya Gong then abandoned Phan. The orphan baby had been unknowingly adopted by chidless Granny Hom. Granny Hom raised Phan in Ratchaburi, a vassal city state of Nakhon Chai Si. One day an elephant of the local lord was in rut and attacked people. Phan went to see the elephant and was able to subdue it. After Ratchaburi lord heard about heroic act of Phan, the lord adopted Phan as his son. Phan wanted to conquer Nakhon Chaisi of Phaya Gong, so he sent a letter to Phaya Gong for war elephant duel battle. Phan killed Phaya Gong, and demand Phaya Gong’s wife to become his queen according to ancient custom. When the queen met Phan, she recognized him to be her son, and told him the truth. Shocked Phan, now became king and named Phaya Phan, executed old Granny Hom for not reveal the truth before he killed his father. After realised that he did a great sin by killing both father and a person who raised him, Granny Hom, in the year 26 BCE Phaya Phan consulted with a group of arhats how to relieve his sin. The arhats recommended Phaya Phan to build a great stupa with great height that birds can fly. Phaya Phan then built a Sri Lanka style stupa by using a very big gong and his bed as foundation and put Buddha’s tooth relic inside. Hundreds years later, the king of Bago wanted the big gong, so he ordered to dig the stupa’s foundation; as a result, both gong and stupa then collapsed. The Bago king tried to rebuild the stupa, so he built Khmer style stupa on the top of old stupa, which was the stupa form until the reign of Mongkut.

Scanned from a film negative. At first I thought the black dots around the stupa (particularly to the right) were marks on the negative, but they’re not. They’re birds.