Here is an odd result of the ongoing border dispute between Croatia and Serbia, two countries separated by the Danube River. Serbia believes the border should follow the river’s path, but Croatia believes the divide should be based on the cadastral boundaries of years past, which followed the Danube’s watershed in the 1800s before hydraulic engineering changed river's course.
Interestingly, this leaves about four square miles of current Croatian territory that Croatia believes actually belongs to Serbia, but Serbia doesn't claim either. The small parcel of land on the west bank of the Danube can thus be classified "terra nullius," or "no man's land." That is, until one man snatched it up, and proclaimed it "Liberland."
In April, 2015, a Czech libertarian named Vít Jedlička declared part of the unclaimed territory along the Danube as a sovereign micro-state, the "Free Republic of Liberland." If formally recognized, the tiny parcel of land would be the third smallest sovereign state, after the Vatican and Monaco, and the youngest country in the world.
Jedlička appointed himself president of the young nation, and named Liberland's two vice presidents, as well as ministers of finance, foreign affairs, interior, and justice. He claimed that Liberland was on its way to satisfying the conditions of statehood as laid out in the Montevideo Convention, and for a time it looked like Liberland had all the characteristics of a legitimate micro-nation. But Croatia didn't agree. In May of 2015, Jedlička and his associates were detained by the Croatian police force.
This, however, played right into Jedlička's hand, as once he was released he used the arrest for publicity of Liberland its fundamental libertarian ideologies, such as a "voluntary tax" system, in which citizens can choose whether or not to pay taxes to the government. Liberland's free market economy is completely unregulated, and all currency is virtual.
As it stands today, not a single member of the United Nations has recognized Liberland as a country, although other self-declared micro-nations, such as the Principality of Sealand and the Kingdom of North Sudan, have in solidarity with the movement to make these nations internationally recognized. The movement may be gaining some ground: Liberland has received over 500,000 applications for citizenship since its inception, and this number is increasing by nearly 500 every day.