Rabaul sits aside a stunning harbor formed from a flooded caldera and six cone-shaped volcanoes, a few of which actively emit clouds of steam and ash. A Japanese stronghold in World War II, Rabaul had miles of tunnels, bunkers and underground pens built to hide soldiers and their weapons from view. Tour the town's open-air market and war museum.

Language: Pidgin

Currency: Papua New Guinea Kina (PGK)