Deep water harbour but volcanic action has had the city/capital moved to Kokapo, on the south side of the harbour area.

On the north east side of Rabaul, in the main waterway at Tavui, is a ledge off the side of the cliff that permitted Japanese submarines to bottom and remain protected during air raids.  Their stores and maintenance facilities were kept in caves and when on the surface, the boats were tied to the Wall.  At a sign of trouble, they just bottomed until it was clear.

New Britain is good for diving and catching Mahi Mahi (dolphin fish).

Enjoyed my visits there when I was an advisor in PNG.