The museum, which retraces the town's history, is located in a former school built in 1833. It is modelled on a Greek temple, according to a design by Bernard Mullins and is flanked by the stone of Birr, an enormous limestone rock, probably once part of a megalithic monument near Seffin. It is said to be the gathering place of the mythical Fianna warriors. It was moved to a County Clare residence in 1828 to be used as an altar stone but taken back to Birr in 1974.