Untouristy nations divide into three categories: (a) dangerous [Somalia]; (b) inaccessible [North Korea]; or (c) move-along-nothing-to-see-here.
The least visited nation in the world, Nauru, fits into that third category:
Nauru is a tiny island nation in the Pacific. The smallest republic in the world covers only 21 square kilometers. There is almost nothing to see there as most of the island (there's only one) is a large open phosphate mine.