131 participants from 28 countries, including 55 mayors and deputy mayors of European cities, gathered in Rotterdam for a Summit of Mayors for the “Alliance of European cities against violent extremism” on 9 November 2016. A joint initiative by the Congress, the City of Rotterdam and the European Forum for Urban Security, the Summit was opened by Ahmed Aboutaleb, Mayor of Rotterdam, Gudrun Mosler-Törnström, President of the Congress, and Roger Vicot, President of the French Forum for Urban Security and Mayor of Lomme. After the Summit, they adopted a declaration reiterating the key role of local authorities as custodians of human rights, democracy and the rule of law at local level. Participants also emphasised the importance of pursuing multi-agency strategies, by developing a plan of action bringing together all local stakeholders involved in preventing radicalisation, allocating resources and co-ordinating action with different levels of government. The cities involved in the Alliance against violent extremism pledged to pool their resources to train both local government staff and other actors working at the forefront to prevent radicalisation.