National Library of Mongolia

Mongolian National Library (Mongolian: Монгол улсын үндэсний номын сан) located in Ulaanbaatar, is the largest and the oldest surviving library Mongolia. It houses over 3 million books and publications, 1 million of which are rare and valuable books, sutras and manuscripts, including the world's only surviving copies of many ancient Buddhist texts.

More information on the Wikipedia page.

The Library's website, in Mongolian, is.