Ross D.
Google
A UNESCO site at Anuradhapura, it was the political and religious capital that flourished for 1,300 years, was abandoned after an invasion in 993. I do not know how you loose a site like this but it was apparently hidden away in dense jungle for many years, the splendid site, with its palaces, monasteries and monuments, is now accessible once again. Leave lots of time to explore and admire.