Libertarian far-right Sławomir Mentzen and hard-left Adrian Zandberg among challengers as country prepares to vote in presidential election

Hidden off a charming market square in central Poland, a bar offers the closest physical experience to walking into the internet.

Stretching incongruously through medieval basements, Pub Mentzen in Toruń feels like it was designed by someone on a full-fat diet of online politics. As you enter, a gallery wall displays mugshots of “customers we don’t serve”, but instead of rowdy patrons, it features Polish political leaders, including at least five prime ministers.