Deep in the mountains north of Savusavu, reachable by 4WD, lie the ruins of Nukubolu, an ancient Fijian village whose stone foundations, terraces and thermal pools are in surprisingly good condition. The setting is lovely: a volcanic crater with steaming hot springs in the background.
The ruins are on the property of the village of Biaugunu, so take a sevusevu (gift) for the chief and ask permission before wandering around. The turn-off is about 20km northwest of Savusavu; continue about 8km inland and over a couple of river crossings. You can also rent a carrier from town to take you there.