1. Vatican City State: Covers 0.44 square kilometers
2. Principality of Monaco: The Principality is overall abounding on the 2.02-square-kilometer area
3. Republic of Nauru: Today, the 21-square-mile kingdom is divided into 14 districts, in which around 10,175 people live
4. Tuvalu: 25 square kilometers accommodate approximately 10,500 inhabitants.
5. Republic of San Marino: 60.57 square meter state in the middle of Italy
Source: Wonder List