It's a move that says as much about Europe's political polarisation along urban and rural lines as it does about the four countries involved.
The liberal-minded mayors of Budapest, Bratislava, Prague and Warsaw have clubbed together in a direct snub to their national governments.
They have pledged to keep their cities open, tolerant and progressive and to work together on issues like climate change, housing and inequality.
All four countries — collectively known as the Visegrad Four — have clashed with Brussels in recent months. The EU condemned the alleged erosion of rule of law and human rights violations in all of them over either reform of the judiciary (Poland), the treatment of minorities and asylum seekers (Hungary and Slovakia) or conflict of interest at the highest level of government (Czech Republic).
They are also among the most critical of EU proposals to tackle the climate emergency and become carbon-neutral by 2050.
The mayoral quartet signed a "free cities pact" on Monday and also called for EU funds to be sent directly to cities.
The four mayors all secured their office under an independent or opposition ticket and their pact "sends a message that we share the same values and that there are voices in our countries that do not identify with populist and nationalist politics," Prague mayor Zdenek Hrib, said on Twitter.
Bratislava mayor Matus Vallo wrote meanwhile that they all felt like their countries were closing in on themselves, "threatening the values of liberal democracy in our countries". He also argued they were best-placed to lead the charge to protect European values of tolerance and openness because "it is in our capitals that the highest concentration of diversity (whether) social, religious, political, ethnic" can be found.
The signing ceremony was held in Budapest, at the Central European University, which was forced to move most of its activities to Vienna, Austria, after Prime Minister Viktor Orban and his ruling Fidesz party passed so-called "anti-Soros" law targeting CEU founder George Soros.
Budapest mayor Gergely Karacsony praised the university for its "modern, open and critical thinking".