The head of the local flower growers’ co-operative, Giorgio Carbone, was a placid figure with a big black beard. He grew mimosa flowers and lived in a small hilltop town in northwestern Italy, an ancient jumble of narrow cobbled streets, wooden shutters and wrought-iron balconies.

Carbone was very keen on local history. He spent many hours in state and church archives painstakingly reconstructing the town’s 1,000-year story. In 1079 Seborga was designated an imperial principality of the Holy Roman Empire. It remained independent for more than 600 years, until it was sold to the House of Savoy, a transaction that was not registered.

This error was subsequently compounded. When the great powers of Europe settled the continent’s boundaries at the Congress of Vienna in 1815, Seborga was not mentioned. When the many small states on the Italian peninsula were unified to form Italy in 1861, Seborga was not mentioned. In 1946, after the last Savoy king abdicated and Italy became a republic, again Seborga was not mentioned.

In 1995 Carbone put it to the good people of Seborga that their town was not, after all, a part of Italy. In a local referendum, they voted 304 in favour, four against, to ratify Seborga’s independence, which, according to Carbone, it had never lost. Seborgans elected Carbone to represent them. Their kindly ruler held court at the Bianca Azzura bar, often wearing a sword and rosette medallions. He adopted a motto for the principality: Sub umbra sede (Sit in the shade).

You may well scoff. Needless to say, the Italian government refuses to recognise the Principality of Seborga, insisting its citizens still pay their taxes to the authorities in Rome. This they do, but it doesn’t detract from their feeling of group identity. After all, Seborga’s history of independence is rather longer than Italy’s, even if it is now a matter for debate.

Seborga’s kindly ruler adopted a motto for the principality: Sub umbra sede (Sit in the shade)

Establishing what constitutes a country is not straightforward. The concept is old but also notoriously slippery. As soon as you think you have a clear definition you run into exceptions and anomalies.

One answer might be that all “real” countries have membership of the United Nations. But this is not definitive. Taiwan was a UN member until asked to leave in 1971; Israel has been a UN member since 1949, but more than 30 other UN states refuse to recognise Israel’s existence.

Many dictionaries, under the entry for “nation”, talk about a body of people that is sufficiently conscious of its unity to form a government. These are also essential criteria – along with a claim to territory – for statehood, according to the Montevideo Convention, which provides a widely accepted legal definition. So just because no “real” country recognises your existence doesn’t mean you don’t exist. Ask the Seborgans, Taiwanese or Israelis.

Other claims to nationhood have still deeper roots. In southernmost South America, the Mapuche people enjoyed 10,000 years of self-rule – never conquered by either Inca or Spanish empires – until the last century saw them being suppressed and sidelined. But now in both Chile and Argentina, governments have recognised indigenous peoples’ rights, including the right to land.

Seborga and Mapuche. The names may sound fictional, but they are undeniably real places, occupied by patriotic citizens. They comprise part of a shadowy, parallel world of unrecognised countries, a world of wannabe nations that, at least for now, exist only in the minds of the people who live there.

An Atlas of Countries That Don’t Exist by Nick Middleton is published by Macmillan, £20. To order a copy for £15, go to bookshop.theguardian.com