1.
hall; building; large facility
A suffix attached to names of large buildings or public facilities such as museums, libraries, embassies, and hotels. Also used as a standalone noun meaning a large building or mansion.
Usage
Most commonly encountered as a suffix in compound words naming large buildings or public facilities. Rarely used alone in modern Japanese.
The reading 館 exists as a separate word meaning mansion or manor house, with a more archaic or literary feel.