Area at Rabaul, on the northern shore of Simpson Harbor, at the edge of the Lakunai Airfield. This area has natural hot springs that were used by the Japanese as baths. They constructed ceramic tubs and fixtures still present to this day.

Sulphur Creek Seaplane Base (Rabaul / Simpson)
Japanese seaplane base and servicing area

Japanese Volcano Observatory
The Japanese Navy took an interest in seismic and volcano activity at Rabaul, and how it might impact ship movements. Civilian Dr. Takashi Kizawa of the Japanese Central Meteorological Observatory was assigned to Rabaul in May 1942. The Japanese Army built a volcano observatory at the northern edge of Sulphur creek, with two seismographs and tromometer housed in an underground shelter. Bombing made later readings imprecise, and forced it to be relocated. The only activity observed was November 24, 1943 minor eruption. Hit several times by bombs and rebuilt, Kizawa moved to tunnels dug into the ridge beneath Tovanumbatir. Later, he established a new facility near Vunakanau in December 1944 to January 1945, but achieved poor readings. Dr. Kizawa survived the war, was repatriated in 1946 and lives in retirement in Funabashi City, near Tokyo. Reference: Volcano Town