Aside from the Artic and a patch of desert between Sudan and Egypt, there is only one piece of land in the world that is not claimed by any sovereign state. Gornja Siga is a seven square kilometre patch of uninhabited forest on the Croatian side of the Danube River. The border between Croatia and Serbia is disputed by the two countries. The Croatian government, which thinks the border should follow the Danube’s 19th century course, says Gornja Siga belongs to Serbia. Serbia says it belongs to Croatia. That makes it a terra nullius: sovereignty over it is claimed by no one.

No one, that is, until 2015, when a 30-year-old libertarian political activist from the Czech Republic called Vit Jedlicka stuck a flag in the ground and declared it to be the "The Free Republic of Liberland". He quickly rustled up a provisional government and released a constitutional document setting out how this new country would be governed: voluntary taxation, an almost non-existent government, zero restrictions whatsoever on speech or information. And you can do anything you want, as long as you don’t physically harm other people. The freest country in the world, says Vit. The first truly libertarian state. Tens of thousands of people applied for citizenship almost immediately.