3. Nauru
Area: 8.1 sq mi
The Republic of Nauru or Pleasant Island is one of the smallest countries in the world located in the Central Pacific. It’s the third country on our list right after Vatican City and Monaco. It had a large deposit of phosphate rocks that were mined and exported. It made Nauru the wealthiest country in the world in terms of GDP. The deposits exhausted and Nauru is now struggling to save its environment as well as its economy.