Records suggest that the original was quite spectacular, with some 4,000 trees needed to complete its construction.
The dozen pillars that supported the interior were each 100 feet tall and the building's exterior was made entirely of wood.
The impressive scale of the temple didn't sway the Black Flag invaders, who razed it in 1887. A decade later work began to rebuild the temple using brick and plaster, much to the relief of Luang Prabang's remaining forests. While the new structure tries to recreate the original style in brick, featuring many wooden balustrades in the windows, it doesn't really pull it off. Nevertheless the site remains an important repository of religious art, including a large number of cast Buddha statues.
Today, the main attraction within the compound is the That Pathum (Stupa of the Great Lotus) which sits in front of the sim. It's more popularly known as That Makmo -- the watermelon stupa -- for its resemblance to the fruit. Also destroyed (and pillaged) during the Black Flag invasion, the stupa was rebuilt in the late 1920s. It's adjacent to Wat Aham and they are usually visited together.