The Penang War Museum occupies Bukit Batu Maung, a 20-acre hilltop on the southern tip of Penang island that the British fortified in the 1930s as a secondary defence battery against attack from the sea. The fort was overrun within days when Japanese forces invaded in December 1941 and was used through the occupation as a base and interrogation centre. After the war it was abandoned to the jungle, and was only rediscovered and restored in the late 1990s.
The site is now an outdoor museum that combines surviving British military infrastructure — gun emplacements, ammunition stores, an underground tunnel network, the original officer's quarters — with reconstructed Japanese-period elements including a torture room, a beheading site and several memorials. It is a darker, more atmospheric historical experience than anything in central Georgetown, and a real reminder of the brutality of the occupation. Allow two to three hours. Reach it by Grab from the centre (around 30 minutes); there is no good bus option.