trying to debunk the 'fountains that still work after 1500 years' Sigiriya thing and I made it worse for myself

Ok so the viral claim going round is that Sigiriya in Sri Lanka has fountains built by King Kashyapa around 477 AD that STILL shoot water today when it rains, no pump, no nothing, 5th century plumbing outliving every empire since. Sounded like the usual 'ancient aliens' inflation so I started diggin……