The Boudhanath, (also written Bouddhanath, Bodhnath, Baudhanath or the Khāsa Chaitya), is one of the holiest Buddhist sites in Nepal, along with Swayambhu. It is a very popular tourist site. Boudhanath is known as Khāsti by Newars and as Bauddha or Bodhnāth by speakers of Nepali. Located about 11 km (7 mi) from the center and northeastern outskirts of Kathmandu, the stupa's massive mandala makes it one of the largest spherical stupas in Nepal. Boudhanath became a UNESCO World Heritage Site in 1979.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): When did UNESCO make Boudhanath a World Heritage Site?
1979