Opened as recently as 1991, Powys County Archives Office is located in Llandrindod Wells, and serves as the official repository for the records of the modern county of Powys (first established in 1974) and the three former counties of Breconshire, Montgomeryshire and Radnorshire. Powys Archives forms part of Powys Library, Archives and Information Service.

http://www.powys.gov.uk/en/archives/find-archives-local-records/

The Archive has relocated recently and it now based  in:

Unit 29 Ddole Road Industrial Estate, Llandrindod Wells, LD1 6DF