Local authorities are on the front line when it comes to the prevention of radicalisation leading to terrorism and violent extremism. Repression alone cannot solve the problem. Prevention, signalling and providing programmes to help (potential) extremists to abandon violent extremism are also necessary. These actions must be organised at the local level and mobilise civil society. The cities’ proximity to citizens puts them in a unique position to build resilience and counter violent extremism through integrated, multi-agency strategies.The Congress of Local and Regional Authorities of the Council of Europe and the European Forum for Urban Security, in partnership with the Strong Cities Network, are bringing together European mayors and other local and regional elected officials in order to make their needs heard and help them strengthen their capacity to prevent and deal with all forms of violent extremism.This conference will also be the starting point of the Congress-Efus joint initiative “Towards an alliance of European cities against violent extremism”, which aims to provide a platform to facilitate inter-city exchange at the political and subsequently technical level, and mobilise European local and regional authorities.The conference in Aarhus will be hosted by both the Mayor of Aarhus and the Mayor of Rotterdam and organised in partnership with the Strong Cities Network.