From the English Wikipedia page .
The National Archives of Hungary (in Hungarian: Magyar Országos Levéltár) were created in 1756. They were first located in Bratislava (now capital of Slovakia). In 1784, they were transferred to Buda.
The Hungarian National Archives (until 2012 the National Archives of Hungary) is a state public collection institution that keeps records of national treasures. Its buildings are located in Budapest, at the Bécsi Gate Square of District I , on Daróczi Street and at Lángliliom Street in Óbuda . The institute holds a total of 73 kilometers of records, more than 63.5 million microfilms and countless seals, maps, photos, plans, diplomas. The activities, tasks and scope of the archives are defined in Act LXVI of 1995. (Law on Archives).
The website, in Hungarian, is