The venerable New Guinea Club, built in 1937, is now a museum about the history of Rabaul. Lots of photos. Very hot.
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The General led the Japanese South Pacific campaign. He was eventually shot down by the Americans after flying out of Rabaul on an inspection tour to the Solomon Islands. It's small and there's nothing in it but you can visit his underground command post.
The observatory's work in keeping watch on the volcanos was the reason why no one died in the 1994 eruption. There is a lookout here with a great view over the town, bay, and volcano.
At the end of the road is a parking lot where you pay. You can take a look at the hot springs (don't fall in, they're deadly) and get a really good view of the volcano and the ash deposits. Locals will be selling handicrafts. Climbs start from here.
There are around 700km of tunnels in the hills that surround Rabaul's Simpson Harbour. Accommodation, hospitals and hiding places for barges were built in them. Some of the barges can still be seen in this tunnel at Karavia.
A collection of Japanese war relics and a few photographs and trinkets.
Maintained by the Australian War Graves Commission this is the final resting place for servicemen from many countries who died in WWII. There is also a Japanese War Memorial at a former sea-plane base.